Preheat the oven to 350F degrees. Spray a 9" high sided round pan or springform pan with nonstick cooking spray. Note: If using a springform pan, you will need to place a piece of foil or bake on a sheet tray to catch any of the butter/sugar mixture that may leak out the bottom.
In a medium bowl, whisk together butter and brown sugar. Spread into the bottom of the prepared pan.
Top the brown sugar mixture with sliced bananas in an even layer. Set aside.
In a large bowl, whisk together all-purpose flour, baking powder salt, set aside.
In another bowl, beat together unsalted butter, granulated sugar, egg and vanilla extract until combined.
Add in the flour mixture to the butter mixture and beat until combined. It will look crumby at this point which is normal.
Lastly, add in milk and beat until incorporated.
Spoon the batter over the bananas and gently spread using an offset spatula as the batter is thick.
Bake in the oven for about 35-40 minutes until golden or until a toothpick inserted into the center comes out clean. Please note, oven times vary so please check with a toothpick first to ensure doneness as it may take longer in your oven.
Remove from the oven and let cool in the pan for about 10 minutes (don’t skip this essential cooling down time). Run a knife along the pan's edge to ensure it is released before inverting it over a serving platter.
Let cool and dust the top with powdered sugar and serve each slice with a dollop of Cool Whip (optional).
Notes
Please refer to my FAQ’s (Frequently Asked Questions) and ingredient list above for other substitutions or for the answers to the most common questions.
As with all baked goods, oven times will vary. It can depend on so many factors like if you used a metal or ceramic baking dish or a gas or electric oven or what rack you baked it on. It may take longer in your oven so always make sure you test the center of the cake with a toothpick. If there is any batter on the toothpick, it’s not ready.
Make sure you use enough bananas to cover the bottom of the pan.
Make sure you let this cool for at least 5-10 minutes before turning out onto a serving dish. Otherwise, the brown sugar mixture won’t have time to set up properly.
If you have any of this cake remaining, you can store it at room temperature (covered with plastic wrap or in an airtight container) for 2-3 days. Or you can refrigerate it properly and store it for 5-6 days.