Preheat oven to 375 degrees.

Grease a round 9″ spring form pan.

Prepare the crumb topping by pulsing all ingredients in the bowl of a food processor and set aside.

In a large bowl, mix flour, baking powder, salt, cinnamon and nutmeg.

In the bowl of a food processor, mix sugar, butter, egg, and vanilla until well combined.

Pour sugar and butter mixture into flour and stir until combined, add buttermilk then mix again.

Spread half of the batter on the bottom of the spring form pan, then top with sliced banana and cover with the remaining batter.

Top the cake with the crumb by gently pressing it into the batter.

Bake for 40-50 minutes or until a knife inserted into the middle of the cake comes out clean.

Let cake rest at least 15 minutes, so that the crumb’s crystalline edges are able to harden and separate from the pan’s edge.

Release the spring and let stand until cool, or serve warm.