Ingredients:

  • 1/2 cup unsalted butter, melted
  • 3/4 cup brown sugar, packed
  • 1 large egg, room temperature
  • 1 tsp vanilla extract
  • 3 medium overripe bananas, mashed (approx. 1 1/2 cups)
  • 2 cups all-purpose flour
  • 1 tsp baking powder
  • 1 tsp baking soda
  • 1/2 tsp salt
  • 1 tsp ground cinnamon
  • 1/2 cup all-purpose flour (for streusel)
  • 1/2 cup brown sugar (for streusel)
  • 1 tsp ground cinnamon (for streusel)
  • 4 tbsp cold unsalted butter, cubed

Instructions:

  1. Preheat the oven to 350°F (175°C). Grease a 9x9 inch pan and line it with parchment paper, leaving an overhang on the sides.
  2. In a large bowl, whisk the melted butter and brown sugar until smooth. Beat in the egg and vanilla extract until the mixture is glossy.
  3. Stir in the mashed bananas until fully integrated.
  4. Sift the all-purpose flour, baking powder, baking soda, salt, and cinnamon directly into the wet mixture.
  5. Gently fold the ingredients together with a spatula until no streaks of flour remain, being careful not to over-mix.
  6. In a medium bowl, whisk together the streusel flour, brown sugar, and cinnamon.
  7. Add cold, cubed butter to the streusel mixture and rub it in with fingertips or a fork until the mixture resembles coarse, sandy pebbles.
  8. Spread the batter evenly into the prepared pan and sprinkle the streusel mixture generously over the top.
  9. Bake for 35–40 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
  10. Allow the cake to cool in the pan for at least 30 minutes before slicing.