1 1/2 cups gluten-free cake flour
1/2 teaspoon xanthan gum (omit if your blend already contains it)
1 1/2 teaspoons baking powder
1/4 teaspoon baking soda
1 teaspoon ground cinnamon
1/4 teaspoon kosher salt
1/4 teaspoon cream of tartar
1/4 teaspoon freshly grated nutmeg
3/4 cup sugar
6 tablespoons unsalted butter, at room temperature
2 extra-large eggs at room temperature, beaten
3/4 cup apple cider
Cinnamon-sugar mixture, to taste, for rolling the doughnuts
Preheat your oven to 325°F. Grease a doughnut pan (I have a 6-doughnut pan made by Wilton) and set it aside.
In a large bowl, place the cake flour, xanthan gum, baking powder, baking soda, 1 teaspoon ground cinnamon, salt, cream of tartar, nutmeg and 3/4 cup granulated sugar, and whisk to combine well. Add the butter, eggs and cider, and mix to combine well. The batter will be thin. Continue to mix until it begins to thicken.
Transfer the batter to a piping bag fitted with a small plain tip or a squeeze bottle. If using a piping bag, be careful not to let the batter come out of the tip where you don’t intend it to. Squeeze the batter into the prepared doughnut wells until they are each about 2/3 of the way full. Shake the pan back and forth horizontally until the batter is in an even layer in each well.
Place the pan in the center of the preheated oven and bake until the tops of the doughnuts spring back when pressed (about 8 minutes). The underside will be browned, but the tops will still be relatively pale. Remove the pan from the oven and allow the doughnuts to cool for about 3 minutes, or until they are no longer too hot to touch.
While the doughnuts cool slightly, place the cinnamon sugar mixture in a shallow pan or bowl. Gently remove the slightly cooled (but still warm) doughnuts from the doughnut pan with your fingertips and turn them around in the cinnamon sugar until they are well-coated on all sides. Place the finished doughnuts on a clean sheet of parchment paper.
Repeat the above steps for the rest of the doughnut batter and resulting doughnuts.
Store leftovers in airtight container in the refrigerator. You can also freeze any remaining leftovers in a sealed, freezer-safe container.