In a medium bowl, combine rice flour, tapioca starch/flour, potato starch, baking powder, salt and nutmeg.

In a large bowl, beat butter and sugar together until sand-like. Add egg yolks, one at a time, mixing until evenly distributed. Add dry ingredients and sour cream and mix until combined.

Scoop dough into a big ball in the center of the bowl and cover with plastic wrap. Refrigerate 1 hour.

Dust a clean work surface with gluten-free flour. Drop chilled dough on floured surface and roll it out to ½-inch thickness using a floured rolling pin. Use a donut cutter or two different-size biscuit cutters to cut out donuts. Save the holes to fry separately. Roll remaining dough scraps back into a ball and re-roll to ½-inch thickness. Cut out donuts, repeating the process until all dough is used. If donut cutter sticks, dip it in gluten-free flour and try again.

Pour 2 inches of oil into an electric fryer and heat to 325°F.

Gently lower 2 to 4 donuts or donut holes, one at a time, into preheated oil. Fry 2 minutes or until golden brown. Using a slotted spoon, carefully flip donuts or donut holes over. Fry 2 more minutes or until brown. Remove donuts or donut holes and drain on a paper towel-covered plate. Repeat until all donuts and donut holes are cooked.

To make the glaze, whisk together confectioners’ sugar, milk, vanilla and salt in a small bowl until smooth. To remove stubborn lumps, microwave glaze 30 seconds and stir.

Dip tops of each donut into glaze and transfer to a wire rack placed over a sheet pan (to catch any drips). Let sit 15 minutes or until glaze sets.