In a mixing bowl, combine the butter, sugars, eggs, vanilla, molasses, and bourbon. Using a hand mixer, mix on low-medium speed until combined.
Add in the flour, baking soda and powder, salt, and cinnamon. Mix on low speed until incorporated.
Fold in the bananas and nuts.
Transfer the batter to a grill-safe loaf pan that's been greased or sprayed with baking spray.
Bake indirect in a preheated smoker/grill on 250 degrees Fahrenheit for about 2 hours, or until a toothpick comes out clean when inserted in the center.
Remove from heat (pan will be hot, so use caution and use your oven mitts!). Allow to cool. Cut into slices and serve.