Preheat the oven to 350 degrees. Line an 8x8 square pan with parchment paper so that it hangs over two sides.
Place the bananas in a bowl and mas thoroughly with a fork. Mix in the sugars and the oil. Stir well.
Add the gluten free flour blend, baking soda, baking powder, and salt. Add the non-dairy milk, vinegar, and vanilla extract. Stir well.
Pour the batter into the prepared pan. Bake at 350 degrees for 28-34 minutes or until a toothpick inserted in the center comes out clean.
Let the cake cool completely before frosting.
Cream the vegan buttery spread in a large bowl. Add a little bit of the confectioner's sugar and cocoa powder. Continue to mix on low speed.
Alternate adding the sugar and cocoa powder and drizzling in the non-dairy milk until the desired consistency is reached. You may need more or less non-dairy milk. The frosting should be easy to spread, but not runny.
Frost the cake once it is cooled. Serve immediately or store in the refrigerator.
Notes
If you would like to make cupcakes with this recipe, line a muffin pan with 10 paper liners and bake at 350 degrees for 16-20 minutes.