Prepare the topping: In a small saucepan or in the microwave, melt ¼ cup of butter. Stir in the brown sugar and mix until fully combined and glossy. Pour this mixture into your greased baking pan, spreading it evenly across the bottom. Arrange the banana slices in a single layer over the brown sugar mixture, covering as much of the base as possible.

Mix the dry ingredients: In a medium bowl, whisk together the flour, baking powder, salt, and cinnamon if using. Set aside.

Cream the butter and sugar: In a large bowl, beat the softened butter and granulated sugar until light and fluffy. This step incorporates air into the batter, helping the cake rise properly.

Add eggs and vanilla: Beat in the eggs, one at a time, making sure each is fully incorporated before adding the next. Stir in the vanilla extract.

Combine wet and dry: Add half of the dry mixture to the wet ingredients, mixing just until combined. Pour in the milk, stir, then add the remaining flour mixture. Be careful not to overmix, as this can make the cake tough.

Assemble and bake: Pour the cake batter over the bananas in the prepared pan and gently spread it into an even layer. Bake in a preheated 350°F (175°C) oven for 35–40 minutes, or until a toothpick inserted in the center comes out clean.

Cool and invert: Let the cake rest in the pan for 10–15 minutes before carefully inverting it onto a serving plate. If any bananas stick to the pan, just place them back on top of the cake.

Serve and enjoy: Serve warm, at room temperature, or even chilled. It’s delicious on its own but even better with a scoop of ice cream or a dollop of whipped cream.