01 -
Heat your oven to 350°F (175°C). Grease a 9×5-inch (23×13-cm) loaf pan lightly with flour or use parchment paper instead. Put it aside for now.
02 -
Melt butter in a big bowl and let it cool a bit. Mix in sugar, then drop in eggs and vanilla. Add flour and baking soda. Gently mix in your mashed bananas just until everything comes together.
03 -
In a little bowl, blend melted butter, white sugar, brown sugar, and cinnamon with a fork until it's thick and fully mixed. If it seems too stiff to swirl, add another spoon of melted butter to get it right.
04 -
Put 1/4 of your batter in the bottom of the pan. Add 1/4 of your cinnamon sugar on top and use a knife or spoon to make swirls. Add more batter, then more cinnamon mix. Keep going with the rest, making big swirls on the top layer.
05 -
Put the pan on a baking sheet and bake for 65-70 minutes until it's golden and a toothpick comes out clean when poked in the middle. Let it sit in the pan for at least 30 minutes before moving to a wire rack to cool all the way.