Preheat oven to 350° F. Line an 8x8 baking dish with parchment paper. Combine dry ingredients in a large bowl. Stir in wet ingredients.
Prepare flax eggs (2 tbsp flax mixed with 6 tbsp water) and let sit.
Combine dry ingredients in a large bowl. Stir in wet ingredients. Add in flax egg.
Pour into pan and bake for 20-25 minutes. Let cool before cutting.
I recommend refrigerating it overnight before cutting for best results. Cut in half and spread frosting on top of one half. Stack the other half on top and top with frosting. Cut into squares and enjoy!