First, add all the dry ingredients into a larger bowl, which are gluten-free oat flour, rice flour, brown sugar, cinnamon, nutmeg, salt, and baking powder.
Then add in soy milk and pumpkin puree. Combine it all well, but do not over mix it.
Pour the batter into a round baking pan (10'') and bake at 150°C (300F) for 30 minutes.
Meanwhile, prepare a butter frosting by mixing all ingredients with a hand mixer until fluffy and creamy.
When the cake is out of the oven and completely cold, cut the round shapes and put butter frosting on the first layer. Then add another layer of cake and finish it off with the last layer of frosting.
You can make five beautiful mini pumpkin cakes out of this recipe. Enjoy!