Preheat oven to 350°F. Prepare two 9-inch round baking pans by lightly greasing them and lining the bottoms with parchment paper.

Sift flour, baking powder, baking soda, salt, and cinnamon into a bowl. In a large mixing bowl, whisk together eggs, sugar, oil, and vanilla until everything is well combined. Scrape the mashed bananas into the mixture and add in milk. Stir until combined.

Starting with half the flour mixture, gently incorporate the dry ingredients into the wet. Repeat with the remaining flour mixture. Set aside while you make the caramel for the topping.

Melt the butter and brown sugar in a sauté pan over medium-high heat, stirring until the mixture comes together. It will take a couple of minutes to incorporate the butter into a unified sauce. Once the sugar and butter have made a sauce, keep cooking and stirring for another couple of minutes to encourage the sugar to melt. (It’s okay if the sauce is still a little grainy when you remove it from the heat.)

Pour the caramel evenly into the two pans. Place the sliced bananas on the caramel, dividing them equally. These will ultimately be the tops of the cakes, so take care to place the slices in a nice pattern.

Divide the batter, adding half to each pan. Place a parchment-lined baking sheet under each pan to catch any drips, and bake for 45 to 55 minutes, rotating the pans halfway through and checking at the 45-minute mark to see if a toothpick or wooden skewer inserted into the center comes out clean.

Allow cakes to cool completely. Run a butter knife around the edge of each cake. To invert, take a plate larger than the cake pan and cover the cake, then flip the plate and pan together and gently ease the cake onto the plate. Serve plain or with soft whipped cream or ice cream.