How to Make It
Preheat the oven to 350°. Grease a 9-by-5-inch metal loaf pan with nonstick spray and line the bottom with parchment paper, allowing 2 inches of overhang on the 2 long sides. Spread the pecans on a baking sheet and toast for about 7 minutes, until lightly browned and fragrant. Let cool.
In a medium bowl, whisk the flour with the baking powder, baking soda and salt. In another bowl, beat the eggs with the banana, sour cream, vanilla and banana liqueur until combined.
In a stand mixer fitted with the paddle or using a hand mixer, beat the 5 tablespoons of butter with the granulated sugar at medium speed until fluffy, about 2 minutes. At low speed, gradually beat in the wet ingredients until incorporated, then beat in the dry ingredients until just combined; fold in the toasted pecans.
Scrape the batter into the prepared pan and bake in the center of the oven for about 1 hour and 30 minutes, until a toothpick inserted into the center of the loaf comes out clean. Transfer the pan to a rack and let cool for 45 minutes, then turn the bread out onto the rack and let cool completely. Dust the top with confectioners’ sugar, cut into slices and serve with softened butter.