Roasted Banana Buttermilk Sheet Cake with Brown-Butter Frosting and Pecans

Why You’ll Love This Recipe

• Roasting the bananas concentrates their sweetness for deep, caramelized banana flavor.
• Buttermilk keeps the sheet cake tender, moist, and fluffy without being heavy.
• Nutty brown-butter frosting adds a toasty, bakery-quality finish.
• Toasted pecans and a whisper of cinnamon provide crunch and cozy warmth.

Grocery List

• Produce: Very ripe bananas (4 large)
• Dairy: Buttermilk, unsalted butter, eggs
• Pantry: All-purpose flour, granulated sugar, light brown sugar, powdered sugar, baking powder, baking soda, vanilla extract, neutral oil, fine salt, ground cinnamon, pecans

Full Ingredients

Roasted Bananas

• 4 large very ripe bananas (about 1 lb/450 g), unpeeled

Cake Batter

• 2 cups (240 g) all-purpose flour
• 1 cup (200 g) granulated sugar
• 1/2 cup (100 g) light brown sugar, packed
• 1 tsp baking powder
• 1 tsp baking soda
• 1/2 tsp fine sea salt or kosher salt (fine)
• 1/2 tsp ground cinnamon
• 1/2 cup (120 ml) neutral oil (such as canola or grapeseed)
• 2 large eggs, room temperature
• 3/4 cup (180 ml) buttermilk, room temperature
• 2 tsp pure vanilla extract
• Mashed roasted bananas from above (about 1 1/2 cups/340 g)

Brown-Butter Frosting

• 12 tbsp (170 g) unsalted butter
• 3 1/4 cups (390 g) powdered sugar, sifted
• 1/2 tsp fine sea salt
• 2 tsp pure vanilla extract
• 4–6 tbsp (60–90 ml) buttermilk, as needed for consistency
• 1/8 tsp ground cinnamon

Topping

• 1 cup (110 g) pecan halves, toasted and roughly chopped
• Optional: Pinch of flaky sea salt for finishing

Step-by-Step Instructions

Step 1: Roast the bananas until jammy

Preheat the oven to 400°F (200°C) with a rack in the center. Place the unpeeled bananas on a parchment-lined sheet pan and roast until the skins are very dark and the bananas are soft and fragrant, 15–20 minutes. Cool 10 minutes, then peel and mash until mostly smooth. You should have about 1 1/2 cups (340 g) mashed roasted banana. Set aside to cool to just warm.

Step 2: Toast pecans and prep the pan

Reduce oven temperature to 350°F (175°C). Spread pecans on a small sheet pan and toast until fragrant and a shade darker, 7–8 minutes. Cool, then roughly chop. Meanwhile, grease a 9×13-inch (23×33 cm) metal baking pan and line the bottom with a parchment sling for easy removal. Lightly grease the parchment as well.

Step 3: Whisk the dry ingredients

In a large bowl, whisk together flour, granulated sugar, brown sugar, baking powder, baking soda, salt, and cinnamon until no streaks remain. This evenly distributes the leaveners and prevents clumps.

Step 4: Whisk the wet ingredients and combine

In a medium bowl, whisk oil, eggs, buttermilk, and vanilla until smooth. Pour the wet ingredients into the dry and stir gently with a spatula until a few flour streaks remain. Fold in the mashed roasted bananas just until incorporated. Do not overmix; a few small lumps are fine.

Step 5: Bake the sheet cake

Scrape the batter into the prepared pan and smooth the top. Bake at 350°F (175°C) for 25–30 minutes, until the top springs back and a toothpick inserted in the center comes out clean or with a few moist crumbs. Cool in the pan on a rack for 45–60 minutes until completely cool to the touch before frosting.

Step 6: Brown the butter and make the frosting

In a light-colored saucepan, melt the butter over medium heat. Continue cooking, swirling occasionally, until the milk solids turn golden brown and smell nutty, 4–6 minutes. Immediately pour into a heatproof bowl, scraping in the browned bits. Cool to room temperature until slightly thickened but still pourable, 15–20 minutes.

In a stand mixer bowl (or with a hand mixer), combine the browned butter, powdered sugar, salt, vanilla, and 4 tbsp (60 ml) buttermilk. Beat on low to combine, then on medium until fluffy and smooth, 2–3 minutes. Add additional buttermilk 1 tbsp at a time until spreadable. Beat in the 1/8 tsp cinnamon.

Step 7: Frost, garnish, and serve

Spread the brown-butter frosting generously over the cooled cake, creating swirls. Sprinkle with the chopped toasted pecans and a tiny pinch of flaky salt if using. Slice into 15 squares and serve. The cake tastes even better after 30 minutes as the flavors meld.

Pro Tips

• Roast bananas in their peels to avoid watery mash and to deepen caramelized flavor.
• For the fluffiest crumb, measure flour by weight or fluff, spoon, and level. Overpacking flour makes cake dense.
• Use room-temperature eggs and buttermilk for a smoother batter that bakes evenly.
• Let brown butter cool before beating or the frosting can separate; if it does, chill briefly and rebeat.
• Save a tablespoon of chopped pecans to sprinkle over slices just before serving for extra crunch.

Variations

• Chocolate chip twist: Fold 1 cup (170 g) semisweet chocolate chips into the batter before baking.
• Maple-brown butter frosting: Replace 2 tbsp of the buttermilk with pure maple syrup and finish with a light drizzle on top.
• Banana cupcakes: Divide batter into 24 lined muffin cups; bake at 350°F (175°C) for 17–20 minutes, then frost.

Storage & Make-Ahead

Cover and store the frosted cake at cool room temperature for up to 2 days or refrigerate up to 5 days (bring to room temp before serving). Unfrosted cake can be wrapped and frozen up to 2 months; thaw overnight in the fridge. Frosting can be made 2 days ahead; refrigerate covered and bring to room temp, then rebeat with a splash of buttermilk. Toast pecans the day you serve for best crunch.

Nutrition (per serving)

Approximate values for 1 of 15 slices: 480 calories; 25 g fat; 60 g carbohydrates; 4 g protein; 2 g fiber; 370 mg sodium; 38 g sugars.