Banana coffee cake is a soft, moist and fluffy banana cake layered with a sweet cinnamon sugar, topped with crunchy streusel. This banana crumb cake is perfect for breakfast or brunch.
In a large bowl, whisk together the flour, brown sugar, granulated sugar and ground cinnamon for the streusel topping. Work in the melted butter a little at a time until a sand like texture develops. In another bowl whisk the light brown sugar and cinnamon together until well combined. Set aside for now.
In a large mixing bowl, mash the bananas until mostly smooth with very few lumps. Whisk in the melted butter, light brown sugar, sugar, eggs, vanilla extract and buttermilk until well combined. Whisk in the dry ingredients until just combined.
Evenly spread half banana cake batter into the prepared pan. Top the banana cake layer with the cinnamon sugar. Repeat with a second layer of coffee cake. Top with the streusel.
Bake the coffee cake for 45 - 60 minutes or until a toothpick inserted into the center of the banna crumb cake comes out clean or with a few moist crumbs. Cool the pan in the pan for 15-20 minutes. Gently lift the coffee cake out of the pan using the parchment paper.