Preheat & Prepare: Preheat oven to 180°C (350°F). Grease a 9-inch cake pan.
Mash Bananas: In a large mixing bowl, mash the ripe bananas until smooth.
Mix Wet Ingredients: Add melted vegan butter, unsweetened soy milk, and ground flaxseeds. Stir well.
Combine Dry Ingredients: In a separate bowl, whisk together flour, baking powder, baking soda, salt, and sugar.
Mix the Batter: Gradually fold the dry ingredients into the wet mixture. Stir until just combined. Do not overmix.
Add Mix-Ins (Optional): Fold in walnuts, chocolate chips, cinnamon, or dried fruit for added flavor.
Bake: Pour batter into the prepared cake pan and bake for 45-50 minutes or until a toothpick inserted in the center comes out clean.
Cool & Serve: Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely. Slice and enjoy!