Preheat oven to 350 degrees and place two cupcake liners in muffin pans or use a silicone pan.
Prepare flax egg by whisking flax seed and water together in a small bowl. Set aside 5 minutes to thicken.
Combine brown rice flour, pumpkin, peanut butter, baking powder, flax egg, and water and stir to thoroughly incorporate.
Divide batter between cupcake liners. They will be full.
Bake for 18-20 minutes or until a toothpick inserted comes out clean.
Allow to cool completely before frosting.
Whisk together peanut butter and pumpkin and frost the pupcakes.
The batter did stick to the paper liners because I didn't wait for them to cool completely. So don't be like me, be patient!