Bake

• Preheat your oven to 325F and grease and line an 8×8 baking pan, allowing the paper to hang over the sides for easy removal.
• Start by making the crumble – Combine the flour, cinnamon, and sugars in a bowl. Then mix in the melted butter. The mixture should resemble wet sand. Place the bowl in the refrigerator to chill while the rest of the cake is made.
• For the banana cake, whisk together the flour, baking soda, and salt in a medium bowl. Set aside.
• In a large mixing bowl, whisk together the sugars and butter.
• Once fully combined, whisk in the sour cream, egg, vanilla, and mashed banana.
• Gently mix in the dry ingredients using a rubber spatula.
• Spread half of the batter into the pan. Combine the cinnamon sugar mixture and sprinkle an even layer on top.
• Cover with the remaining batter and gently spread it even.
• Remove the crumble from the refrigerator. It should now be cold and firm. Crumble it on top in an even layer.
• Bake for 40-45 minutes or until a toothpick in the center comes out clean with a few moist crumbs.
• Allow the cake to cool for about 30-40 minutes.
• While it cools, whisk together the powdered sugar and milk to make the icing. It should make a glue-like consistency. If it’s too thick, add ½ tablespoon of milk at a time until it turns smooth.
• Drizzle the icing on top of the slightly warm cake and enjoy!