Preheat your oven to 350°F (175°C).

In a round or square cake pan, combine melted butter and brown sugar over low heat until melted and frothy, then remove from heat.

Sprinkle cinnamon into the butter and brown sugar mixture if desired.

Arrange sliced bananas over the caramel mixture in the pan.

In a large bowl, mix flour, granulated sugar, baking powder, and salt.

In another bowl, combine eggs, milk, vegetable oil, and vanilla extract.

Pour the wet ingredients into the dry ingredients and mix until just combined.

Pour batter gently over the banana layer in the pan.

Bake in the preheated oven for 35-40 minutes or until a toothpick inserted in the center comes out clean.

Let the cake cool for about 10 minutes, then run a knife around the edges and flip it onto a serving plate.