Time 1 hour

Serving 12

For the Cake

• ½ cup/115 grams unsalted butter (1 stick), melted, plus more for pan
• 1½ cups/185 grams all-purpose flour
• ¼ cup/50 grams granulated sugar
• ¾ teaspoon baking soda
• ½ teaspoon fine salt
• 1 cup/250 grams mashed banana (from 2 to 3 very ripe bananas)
• ¼ cup/60 milliliters sour cream
• 2 tablespoons dark brown sugar
• 2 large eggs
• 1 teaspoon vanilla extract

For the Glaze

• 4 tablespoons/65 grams unsalted butter (½ stick), cut into pieces
• ⅓ packed cup/70 grams dark brown sugar
• ¼ cup/60 milliliters heavy cream
• Large pinch of fine sea salt
• ¼ cup/30 grams confectioners’ sugar
• Flaky sea salt, for serving

Step 1
Heat oven to 350 degrees. Grease a 9-by-9-inch pan, and then line with parchment paper, letting the two long ends hang over the edges by at least 2 inches.

Step 2
In a large bowl, whisk together flour, granulated sugar, baking soda and salt. Whisk in bananas, melted butter, sour cream, brown sugar, eggs and vanilla.

Step 3
Scrape into baking pan and smooth the top. Bake until the top springs back when lightly pressed in the center, and a toothpick inserted in the center comes out clean, about 25 minutes. Let cool completely.

Step 4
When cake is cool, make the glaze: In a medium or large pot (not a small one because the mixture will bubble up), combine butter, brown sugar, heavy cream and salt. Bring to a full boil and continue to boil over medium heat for 1 minute. Remove from heat and let sit for 5 minutes.

Step 5
Whisk in confectioners’ sugar until smooth, then immediately pour over cooled cake. Spread evenly across cake and let set for at least 30 minutes. Sprinkle with flaky sea salt before serving.