Preheat oven to 380 degrees, lightly grease pan. 

Melt butter and let it cool.

Mash bananas and add lemon juice, set aside.

In a blender mix tofu and water

Mix flour, baking soda, and baking powder, set aside.

In a large bowel mix (by hand or electric mixer) melted butter, sugar and blended tofu until creamy. Slowly fold in half of the flour mixture, then the rest. Add mashed bananas and nuts. 

Pour batter into greased baking pan and bake for 30 to 40 minutes or spoon into cupcake pan (fill up to 3/4 full) and bake for 15 to 20 minutes. Cake is done when toothpick comes out clean. Allow to cool (at least 10 minutes) before slicing.