Banana Cake with Brown Butter Frosting

Steps

1. Preheat the oven to 175°C (350°F). Lightly grease a 23 × 33 cm (9 × 13 inch) baking pan and line the bottom with parchment paper.
2. In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, 2 g of the fine salt, and ground cinnamon until evenly combined and lump-free.
3. In a large mixing bowl, beat 130 g of the unsalted butter at 20–22°C with the granulated sugar and light brown sugar for 3–4 minutes, until very pale, creamy, and fluffy.
4. Beat in the eggs one at a time, mixing well after each addition and scraping down the sides of the bowl so the mixture stays smooth and homogeneous.
5. In a separate bowl, mash the bananas until mostly smooth. Whisk in 150 ml of the whole milk and 5 ml of the vanilla extract until you have a cohesive banana mixture at about 20–22°C.
6. Add one-third of the dry ingredients to the butter mixture and mix on low just until incorporated. Add half of the banana mixture and mix briefly. Repeat, alternating dry ingredients and banana mixture, ending with the dry ingredients and mixing only until a thick, smooth batter forms. Do not overmix to keep the crumb soft and tender.
7. Scrape the batter into the prepared pan and smooth the top into an even layer so it bakes level.
8. Bake for 30–35 minutes, until the top is deep golden, the edges pull slightly away from the sides of the pan, the center springs back when gently pressed, and a toothpick inserted in the center comes out clean or with a few moist crumbs attached.
9. Let the cake cool in the pan for 15 minutes, then carefully turn it out onto a wire rack. Remove the parchment and cool completely to 20–22°C before frosting so the topping does not melt.
10. While the cake cools, place the remaining 120 g unsalted butter in a light-colored saucepan over medium heat. Cook until melted, then continue cooking, stirring frequently, as it foams and the milk solids at the bottom turn deep golden brown and the butter smells nutty. The butter will be very hot (around 120–150°C). Remove from the heat and immediately pour into a heatproof bowl, scraping in the browned bits. Cool to 20–22°C until opaque and spreadable.
11. To make the brown butter frosting, add the powdered sugar, the remaining 1 g fine salt, the remaining 20 ml whole milk, and the remaining 5 ml vanilla extract to the cooled brown butter. Beat for 2–3 minutes, starting on low and increasing to medium, until the frosting is thick, smooth, creamy, and fluffy. It should be easily spreadable but hold soft peaks.
12. Place the completely cooled banana cake on a serving board or platter. Spread the brown butter frosting evenly over the top, creating soft swirls. The finished cake should have a moist, tender, soft crumb with visible banana flecks and a rich, nutty, caramel-like brown butter frosting that is smooth and creamy.
13. Slice with a sharp knife, wiping the blade between cuts for clean pieces. Serve at room temperature for the best flavor and texture.