3 tablespoons (42 g) unsalted butter, at very soft room temperature
2 cups (280 g) all purpose gluten free flour (I used Better Batter), plus more for sprinkling
1 teaspoon xanthan gum (omit if your blend already contains it)
2 teaspoons baking powder
1/4 teaspoon baking soda
1 1/2 teaspoons kosher salt
1 to 2 tablespoons (12 to 24 g) granulated sugar
1/2 cup (120 g) plain Greek yogurt (0%, 2%, or 4% fat)
3/4 to 1 cup (6 to 8 fluid ounces) plain seltzer water
Preheat your oven to 400°F. Using about 2 tablespoons of the butter, grease very well a 12-inch cast iron or another heavy-bottom skillet, and set it aside.
In a large bowl, place the flour, xanthan gum, baking powder, baking soda, salt, and sugar, and whisk to combine well. Add the yogurt and mix a bit to break it up, then add 3/4 of a cup of the seltzer. Mix until the dough comes together, adding more seltzer as necessary to bring the dough together without making it too soft. The dough should be moist to the touch, but not be weepy. Press the dough together with clean hands, then turn it out onto a lightly floured flat surface. Sprinkle the dough lightly with more flour, then knead lightly a few times to help smooth out the dough and press it into a disk. Using a knife or bench scraper, divide the dough into 8 roughly equal portions.
Working with one piece of dough at a time, sprinkle it very lightly with more flour. Form it into a ball by press it together in the palm of your hand, then pinching the ends underneath and rolling it with the side of your palm pressed against the surface and guiding it with your fingertips into a round about 1 1/4-inches in diameter. Place the rounds close to one another in the prepared skillet. Brush the tops and sides with the remaining butter. Place the skillet in the center of the preheated oven and bake, rotating once, for about 25 minutes or until the rolls are dark golden brown on the underside, very lightly golden brown on top and spring back when pressed lightly in the center. Remove from the oven and serve warm.