To prepare the sauce, add all ingredients to the bowl of a food processor and purée until smooth. Set aside.
Preheat oven to 350˚F (180˚C). Coat a 23.5 x 15.2 centimeter loaf pan with nonstick spray and set aside.
In the bowl of a stand mixer fitted with the paddle attachment (or using a hand-held mixer), cream the butter with sugar. Add the eggs.
In another large bowl, add dry ingredients and mix. Fold the flour mixture into the creamed sugar, one cup at a time with a spatula.
In a small dish, whisk together vanilla, buttermilk and liquer. Add to the flour mixture and mix well. Mash the bananas with a fork, fold the bananas into the batter.
Pour batter into the loaf pan and level, place pecans on top (optional). Bake on the center rack of the oven for approximately 45-50 minutes, or until a toothpick inserted in the center comes out clean.
Let the bread cool on a wire rack for ten minutes.
Serve at once with the dipping sauce on the side or pour over the bread for an appealing display.