How to Make It
Preheat oven to 350°F. Grease a 9- x 5-inch loaf pan with 1 tablespoon of the melted butter; dust with 2 tablespoons of the flour. Hold loaf pan upside down, and gently tap on work surface to shake out excess flour. Set aside.
Stir together granulated sugar and 1/2 cup of the melted butter in a large bowl until combined. Add eggs, mashed bananas, sour cream, and vanilla; stir well to combine.
Stir together baking soda, salt, apple pie spice, and 1 1/2 cups of the flour in a bowl. Add to egg mixture; stir until just combined. Spoon mixture into prepared loaf pan.
Stir together pecans, brown sugar, cinnamon, and remaining 2 tablespoons melted butter and 2 tablespoons flour in a bowl until combined. Sprinkle evenly onto batter in loaf pan. Bake in preheated oven until a wooden pick inserted in center of loaf comes out clean, 55 to 60 minutes.
Let loaf cool 10 minutes in loaf pan. Gently turn out onto a wire rack; let cool completely, about 1 hour. To store, wrap in plastic wrap or aluminum foil, and store at room temperature up to 3 days.