- Mash the bananas. Put together the flour, baking powder, baking soda, salt and sugar in a large bowl. Then add the butter and blend until moist and then add 0.25 cup of the buttermilk and combine well. Preheat the oven at a temperature of 300°F.
- Combine remaining buttermilk with the eggs in another bowl and whisk together. Add to the flour mixture and blend. Then put the vanilla and bananas in the mixture and whisk for 1 minute.
- Take a pan of 9-inch * 13-inch * 2-inch size, grease the pan and then place the batter in it. Put together the 4 tbsp flour, brown sugar and 4 tbsp butter, mix them well. Crumble the topping evenly over the batter.
- Place in the oven and bake for 40 minutes. Transfer 'Banana Cake Recipe' to the serving plates and serve.