Grease a 9-inch x 13-inch casserole dish and set it aside.
Make the dough
In the bowl of a stand mixer fitted with the paddle, whisk together the flour, xanthan gum, tapioca starch, milk powder, yeast, cream of tartar, baking soda, and sugar. Add the salt and whisk again.
Add the vinegar, butter, egg, and milk, and mix to combine.
Increase the mixer speed to high and beat for about 3 minutes, until the dough is fluffy and has a shaggy whipped appearance from air being incorporated into it.
Transfer the dough to a sealed container, and refrigerate for 30 minutes to make it easier to handle.
Roll out the dough
Turn the chilled dough onto a lightly floured surface and knead gently to smooth.
Divide in half, keeping one half covered. Roll the other into a 9x12-inch rectangle about ½ inch thick, dusting with flour as needed.
Add the filling and shape
Spread half the softened butter over the dough, leaving a 1-inch border.
In a small bowl, combine brown sugar, cinnamon and flour, and mix to combine without compressing the sugar.
Sprinkle the dough evenly with half the cinnamon and sugar mixture and pat it down gently to help it adhere.
Starting from a short side, roll the dough tightly into a coil. Slice into 6 rolls using floss or a sharp knife.
Place in a greased 9x13-inch pan, 1 inch apart. Press each roll down about ⅓ of the way to flatten slightly.
Repeat with the second half of the dough and the remaining filling.
Let rise
Cover the pan with lightly oiled plastic wrap. Let rise in a warm spot until the rolls are about 50% larger (about 45 minutes).
Bake
Preheat the oven to 350°F.
Remove the plastic wrap and bake for 20 minutes, until risen, lightly golden, and baked through (about 190°F on an instant read thermometer)
Let cool for 5 to 10 minutes before icing or frosting, but no longer.
Optional glaze.
Whisk together confectioners’ sugar and milk until thick but pourable. Add more milk ¼ teaspoon at a time if needed.
Drizzle over warm rolls.
Optional frosting
Beat butter and confectioners’ sugar until smooth. Add cream gradually to reach a spreadable consistency.
Spread generously over warm rolls.
Video
Notes
Flour blend choicesFor best results, use Better Batter original blend or Nicole’s Best multipurpose blend (with xanthan gum added). King Arthur Gluten Free Bread Flour also works, but yields a denser roll, so try adding 2 more tablespoons of milk.Avoid Cup4Cup and Bob’s Red Mill 1-to-1. If using BRM anyway, add 1½ teaspoons xanthan gum.For DIY blend options, see my all purpose gluten free flour blends page.Nutrition information excluding any frosting or glaze.