Gluten Free Rhubarb Crisp Bars | Sweet & Tart Dessert

By Nicole Hunn | Published: June 10, 2022 | Posted In: Bars, Desserts

5 from 17 votes

Prep Time : 20

Cook Time : 45

Serve up smiles when you make this gluten free rhubarb crisp bars recipe. These gf rhubarb bars are sweet and tart, making them the perfect spring treat.

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These gluten free rhubarb crisp bars, packed with a mix of sweet chopped strawberries and tart rhubarb chunks, are made simply with a shortbread base that we turn into a crisp crumble topping. You'll fall in love with all the bright colors, sweet and tart aroma, and mixture of textures!

Rhubarb strawberry crisp bar on small round gray plate

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Why this is the best gluten free rhubarb bars recipe

Even though these jammy rhubarb crisp bars have 3 layers, including a crust, filling, and topping, they couldn't be simpler to make. We start with a simple gf shortbread crust, made mostly of butter, sugar, and an all purpose gluten free flour blend, and then turn about 3/4 cup of that mixture into a simple brown sugary crisp/crumble topping.

Rhubarb alone tends to be super tart, even once it's cooked down to a soft, tender, consistency in the middle of these beautiful tender, nubby gf rhubarb crisp bars. For the perfect balance of sweet and tart, this recipe calls for half fresh chopped strawberries and half fresh chopped rhubarb.

If you long for the most tart desserts, you won't have to change anything in this recipe except to use a full 16 ounces (a pound) of chopped rhubarb. Soothe any last minute doubts that your palate can handle the full rhubarb experience by tossing a tablespoon or two of sugar with the rhubarb before you pile it on top of the crust.

Raw chopped rhubarb stalks in metal mixing bowl

Ingredients for gluten free rhubarb crumble bars

Gluten free flour – The simple shortbread crust of these bars is made mostly of a combination of just the right all purpose gluten free flour blend with plenty of butter, so select your flour blend carefully. I like Better Batter here, since it provides a sturdy base for all of that cooked fruit in the center.
Cornstarch – We add cornstarch to Better Batter to create additional tenderness in the shortbread crust, so it bakes up light but can still hold all that moisture.
Granulated sugar – The only sweetener in the shortbread crust in these bars is granulated sugar, which adds a gentle sweetness and also helps to tenderize the crust.
Salt – Salt not only balances sweetness but brightens the other flavors in these gorgeous bars. I bake with kosher salt or lightly flaked sea salt, which dissolves completely but is coarse enough to make it easier not to overmeasure and end up with an overly salty final result.
Butter – The butter in the crust should be at room temperature, since we want it to combine fully with the sugar and gf flour without making the shortbread greasy. The additional butter we add to the crumble topping is melted to help moisten the brown sugar topping mixture quickly, and then frozen briefly so we can break it into a chunky topping that crisps up in the oven.
Egg yolk – The single egg yolk in the shortbread crust helps hold the shortbread crust ingredients together, and adds richness.
Light brown sugar – The brown sugar added to the crumble topping adds the rich flavor of molasses for a more complex flavor, which also helps the topping brown in the oven.
Ground cinnamon – A touch of ground cinnamon in the crumble topping helps add depth of flavor and differentiate the topping from the other 2 layers.
Vanilla extract – Vanilla extract adds more flavor to the topping and rounds out the flavors along with the cinnamon.
Rhubarb stalks – Rhubarb stalks, which look like red-tinged celery stalks, can be eaten raw, but aren't very pleasant-tasting—until you cook or bake them down into a delicious, jammy mixture. We only use the stalks of rhubarb, never the leaves since they're poisonous.
Strawberries – Sweet summer strawberries are the perfect complement to the tartness of rhubarb. This recipe calls for 8 ounces of strawberries, as hulled, so don't weigh the ingredient until you've removed the tops.

Raw shortbread crust in pan and pan with raw strawberries and rhubarb

Tips for making the best gluten free strawberry rhubarb bars

Fresh vs. frozen rhubarb

I generally bake with fresh rhubarb, which I tend to find available with the leaves already removed. But even in season, fresh rhubarb can be hard to find. If you have frozen rhubarb that's already been chopped, you can use it in place of fresh here.

Don't defrost your frozen rhubarb chunks before adding them to the bars. In fact, keep them in the freezer until you're ready to assemble the raw bars.

How to cut rhubarb for crumble bars

I often find fresh rhubarb in the store that's already been cleaned and chopped into 6-inch stalks. If your rhubarb is still attached to the leaves, remove and discard the leaves (they're not safe to eat due to their relatively high concentration of oxalic acid, making them apparently dangerous for your kidneys), wash and dry the stalks, and chop them into chunks about 1/2-inch (1 1/4 cm) long.

Fresh vs. frozen strawberries

Like using frozen rhubarb, it's fine to use frozen strawberries, as long as they're already hulled and chopped. If you tried to use whole frozen strawberries, you'd need to defrost them to cut them into the chunks we need for the filling of these bars, and they'd end up wilted and flavorless in the middle of your gf rhubarb crisp bars.

How to prepare your strawberries for these bars

You need 8 ounces, by weight, of fresh (or frozen, see above) strawberries that have already had their tops removed. You can chop them after you weigh them, but if you weigh your strawberries and then remove the tops, you'll end up using too little of the chopped berries in your filling.

Let your gf rhubarb crisp bars cool completely

Before cutting or handling these bars after they're finished baking, be sure to let them cool completely. The center is quite wet, and the topping is nubby and designed to have gaps. That means that they're not as stable as, say, gf brownies, so don't handle them until the filling has been allowed to set to room temperature.

Unbaked crumble topping on top of strawberries and rhubarb in metal square pan

How to store gluten free strawberry rhubarb crumble bars

These bars are so tender and moist that they can be stored in a sealed container in the refrigerator for up to a week. When I have leftover rhubarb crisp bars, I like to cut them into small, bite-sized pieces, place them in a sealed container and leave them in the refrigerator for a quick, sweet snack.

Can I freeze my gf rhubarb crisp bars?

You can freeze these bars, but the fruit layer may develop some ice crystals in the freezer, especially if it's exposed directly to the air of the freezer. Wrap the bars very tightly, and let defrost fully at room temperature before serving them.

Gluten free rhubarb bars: substitutions

Dairy free, gluten free rhubarb bars

The only dairy in these gf rhubarb crisp bars is the butter in both the shortbread crust and the topping. You should be able to replace it with vegan butter (my favorite brands are Miyoko's Kitchen and Melt), but they do tend to have some additional moisture so your topping may not hold its shape quite as well.

Egg free, gluten free rhubarb bars

There's only 1 egg yolk in this recipe, and you can replace it with 1 additional tablespoon of butter (vegan butter, if you're avoiding dairy) in this recipe. If you're concerned that your bars may end up feeling a bit greasy, try adding a few drops of lukewarm water to the crust (just enough to help bring the mixture together enough that it holds together when squeezed in your palm).

Vegan, gluten free rhubarb bars

To make vegan gf rhubarb crisp bars, try using the dairy and egg replacement suggestions above. You'll also need to be sure that there's no bone char used to make your sugars.

Strawberry substitutes

You can replace the chopped strawberries here with more chopped rhubarb for a much less sweet, more tart dessert. If you're concerned the bars will taste too tart, try tossing the rhubarb with a tablespoon or two of granulated sugar first.

You might be able to replace the strawberries with fresh blueberries or raspberries in an equal amount. I think peeled, cored, and chopped macintosh apples would be great, too.

Baked strawberry rhubarb crisp in metal pan cut into squares

FAQs

What is rhubarb?

Rhubarb is a fibrous vegetable that is shaped similar to celery, but is usually bright pink and even red. It's the rare type of produce that is really only available in the springtime, when it's truly in season.

Is rhubarb gluten free?

Yes! Since rhubarb, on its own, is just a plain vegetable (although misleadingly classified as a fruit), it's safe on a gluten free diet.

Are rhubarb leaves edible?

No! Both rhubarb leaves and stalks have oxalic acid, a naturally occurring compound that, in higher amounts can lead to kidney stones and other difficulties, but the leaves contain a much higher concentration of oxalic acid. If you purchased your rhubarb with the leaves attached, remove and discard them first.

Should you soak rhubarb before baking?

No! Rhubarb stalks are relatively fibrous, but these bars bake for long enough in a warm oven that the fibers break down enough to make the rhubarb fork tender and delicious. If you were to soak or precook the rhubarb in any way, it would soften too much in the oven.

What's the best flour for this gluten free rhubarb crumble recipe?

I like to use Better Batter classic blend gluten free flour in this recipe (or my mock Better Batter recipe), lightened with a bit of additional cornstarch. If you're using a blend like Cup4Cup that already has a lot of cornstarch, use an additional 1/4 cup (36 g) Cup4Cup instead of the same amount of cornstarch.

What the difference between a gluten free strawberry rhubarb cobbler and a crisp?

A gf cobbler has a pastry topping, which is often bumpy, like a cobblestone street. A crisp, like these gf rhubarb crisp bars, has a smaller, crumbly topping, that gets super crispy on top as the filling bakes.

Why is my gluten free rhubarb crisp soggy?

Assuming you didn't make any ingredient substitutions which might have affected the moisture balance in these bars, if your rhubarb bars are soggy, did you use softened fruit, or chop your strawberries fine so they dissolved during baking?

Do gluten free rhubarb desserts need to be refrigerated?

If you're storing your rhubarb bars in a temperature-controlled kitchen, you don't need to refrigerate them to keep them fresh for a couple days. Just cover them in plastic wrap or put them in a sealed container. For longer storage, or if your environment is hot and humid, to avoid the butter's spoiling, refrigerate the dessert.

Baked rhubarb crisp square image from overhead

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