My gluten free flour mix is 5 cups brown rice flour, 2 cups white rice flour and 2 cups tapioca flour (all mixed together.)
2 eggs, beaten
2 cups buttermilk
1/4 cup butter, melted
5 cups gluten-free rice flour mix (see note)
1 cup sugar
1 teaspoon nutmeg
1/2 teaspoon cinnamon
2 teaspoons baking soda
1 teaspoon baking powder
2 teaspoons salt
2 teaspoons xanthan gum
1/2 cup sugar, set aside in a bowl
Beat the eggs, buttermilk, and melted butter in a large bowl with a whisk.
Combine dry ingredients in a separate bowl. Fold slowly into the wet ingredients, mixing by hand with a wooden spoon. When the ingredients are mostly combined, use your hands to knead a few times to make sure the ingredients are fully incorporated.
Let the dough rest for 15 minutes. Sprinkle extra rice flour mix on your countertop or a large cutting board. Roll out dough to between 1/3 and 1/2 inch thick. If dough is sticky, work in more rice flour blend.
Heat 2-3 inches of canola oil in the bottom of a pot until very hot (375 degrees F).
Cut dough with doughnut cutter OR use a glass, biscuit cutter or jar with approximately 3-inch diameter to cut disks out of the dough and use the cap of the oil bottle to cut out the center hole.
Remaining dough scraps can be rolled into balls ("donut holes") and fried.
Carefully drop each doughnut in hot oil with fingers, being cautious not to splash oil. Cook until golden brown on both sides (just a few minutes). You will need to cook just a few at a time, but the cooking doesn't take long at all so this goes quickly.
Remove donuts from oil with a slotted spoon or spatula, and place on a plate lined with two layers of paper towel or brown paper to absorb oil. While still warm, roll each donut in the bowl of sugar to coat fully. Alternately, you may omit this step and apply a glaze at this time.
Serve while warm.