In a bowl, mix together the flour, baking powder, baking soda, kosher salt, and cinnamon until well combined.
In a separate bowl, mix the brown sugar and butter together until creamy. Add the eggs and mix well.
Mash the ripe bananas well and add to the brown sugar mixture. Mix well.
Fold the flour mixture into the brown sugar and mix well. Add the vanilla extract and mix until well combined. Set aside.
Caramelize the sugar in the loaf pan, cool slightly, and set aside.
In a bowl beat the egg yolks, making sure there are no bubbles and the batter is lump-free. Add condensed and evaporated milk, vanilla extract, and lemon zest. Mix well.
In a loaf pan, coat the bottom with a layer of caramel and allow to set. Strain the leche flan mixture into the pan, filling it up half full.
Slowly add the banana bread batter to the top of the leche flan mixture.
Place pan in a larger shallow pan filled halfway with hot water as a Bain Marie. Place in the oven and bake at 160°C for about 45 minutes. Poke with a stick/toothpick. Take out pan when stick/toothpick comes out clean.
Serving Size 2 loaf pans