Step 1

Preheat oven to 350° F. Grease a 9x13 baking dish or 9-inch springform pan.

Step 2

In a medium bowl whisk together flour, baking powder and salt. In another bowl, mash bananas until smooth. To the bananas, add the butter and beat until well combined. Add sugar, eggs, and vanilla and mix well. Alternate adding a third of the flour mixture and a third of the buttermilk, mixing after each addition until just combined.

Step 3

To make the crumb, cut all ingredients together with a fork or pastry cutter until a coarse crumb forms. Pour half of the batter into the prepared pan. Top with half of the crumb. Cover with the remaining batter and top with remaining crumb. Bake for 50-55 minutes until the center is set and a toothpick comes out clean.

Step 4

Allow the cake to cool at room temperature for 10 minutes. Whisk together the powdered sugar and milk and drizzle on top.