Brûléed Banana Bread

Name: Brûléed Banana Bread
Ingredients: 6 Tbs. (3/4 stick) (3 oz./90 g) unsalted butter, at room temperature; 1 cup (7 1/2 oz./215 g) firmly packed dark brown sugar; 2 eggs, at room temperature; 1/2 cup (4 oz./115 g) sour cream, at room temperature; 1 Tbs. vanilla extract; 5 large very ripe bananas, peeled; 1 1/2 cups (6 1/4 oz./180 g) all-purpose flour; 1 1/4 tsp. kosher salt; 1 tsp. baking soda; 1 tsp. baking powder; 1 Tbs. ground cinnamon; 2 to 3 Tbs. turbinado sugar; Salted butter, at room temperature, for serving