Found this recipe at Amanda's Random Ramblings (cute blog!). I used it to make cupcakes for Emma's third birthday:
1/2 C white rice flour
1/2 C sorghum flour
2/3 C tapioca starch
1/3 C potato starch
1 C white sugar
2 tsp gluten free baking powder
1/2 tsp salt
1 tsp xanthan gum
3/4 C (1 1/2 sticks) softened butter or margarine
1 1/2 tsp vanilla
1/2 C milk (any type, I used rice milk)
Pre-heat oven to 350 degrees. Grease pans or line muffin pans with paper cupcake liners - this recipe makes 18-24 cupcakes, 2 6-inch round layers, 1 9-inch square cake, or 1 10-inch round cake.
Thoroughly combine the first 8 dry ingredients in a bowl.
Place softened butter in bowl of stand mixer and beat until fluffy. Add flour mix gradually to butter, blending on lowest setting until combined, then changing to setting "2" on the mixer until mixture is crumbly, about 1 minute.
In small bowl, lightly whisk eggs and vanilla together. Add eggs to mixer and mix until smooth and thick, about 1 minute. Add milk and mix for 1 more minute. Batter will be light and fluffy.
Spoon into prepared pan(s) and bake until toothpick is clean. Time will depend on the shape of your pan, but should be about 20-22 minutes for cupcakes, up to 45 minutes for a loaf pan.
Allow to cool in pans for about 10 minutes, then remove to a wire rack. Frost when cool. Very good but, like most gluten free baked goods, best when eaten right away. Should be eaten within 24 hours of baking, otherwise it becomes too dry and crumbly.