Preheat the oven to 350 F / 175 C and grease an 8.5x4.5-inch loaf pan with non-stick spray or butter. Set aside.
Mash 1 cup of overripe bananas and combine with 1 Tbsp of lemon juice. This prevents the bananas from browning and brightens up their flavor. Set aside.
Add 1/3 cup oil, 1/2 cup granulated sugar, and 1 large whole egg + 1 egg white into a large bowl. Beat on a medium-high speed for about a minute with either a hand mixer or a stand mixer with a whisk attachment, or by hand with a whisk.
Sift 1 cup of all-purpose flour (the rest of the flour will be added in step 6), 1 1/2 tsp baking powder, 1/2 tsp baking soda, and 1/2 tsp salt into the oil / sugar mixture. Mix on a low speed until just combined. Scrape the sides and bottom of the bowl as needed with a rubber spatula.
Pour in 1/3 cup of buttermilk or whole milk and mix on a low speed until combined.
Add in the remaining 3/4 cup of flour and mix on low just until you can no longer see streaks of flour. The batter will be quite thick at this point.
Mix in the mashed banana/lemon juice mixture on a low speed until it is fully incorporated into the batter. Fold in 1/3 cup of butterscotch chips. Most of the chips will dissolve in the banana bread as it bakes, but they add nice pops of butterscotch flavor. If desired, you can add a few extra butterscotch chips to the top as a garnish.
Pour the batter into the prepared pan and bake on the upper baking rack for 55-65 minutes. Rotate the pan halfway through to help it bake evenly.
Remove the loaf from the oven and let it cool in the pan for 30 minutes. Transfer to a wire rack to finish cooling.