Gluten Free Chocolate Sheet Cake

Preheat oven to 350F. Sift together brown rice flour, tapioca flour, sweet rice flour, and sugar then set aside. Melt butter in a saucepan then stir in cocoa powder. Once incorporated, pour in boiling water and boil for an additional 30 seconds. Remove from heat and cool. Beat eggs and add to buttermilk. Then stir in salt and baking soda. Once cocoa mix is cooled, stir in flour mixture and mix well until smooth. Then stir in buttermilk mixture. Pour into an ungreased baking sheet and bake for 20 minutes.

Frosting:

In a medium saucepan, melt butter then stir in cocoa powder. Remove from heat and stir in remaining ingredients. Spread onto cooled baked cake.