The easiest-ever banana bread recipe would not seem like it could ever require a substitution. But… my go-to recipe asks for sour cream. I don't readily keep sour cream on hand but find that in cake and sweet bread recipes, buttermilk works just as well.
But what is the likelihood (for me) that I would have buttermilk on hand if I had no sour cream? (Very unlikely.) But… there are always ways around these small obstacles.
I had milk that was going to expire the next day and knew I would not be home to use it. I had lemons. Mix 1 cup of milk with about 2 tablespoons of lemon juice and let it sit for five minutes. You get something thick and dangerously close to buttermilk. This is what I used in the banana bread, and it turned out moist and very flavorful. I think I posted this recipe before (as cupcakes) but here it is again (will add an ugly pic or two later). I also think the original posting may have accidentally omitted the sour cream in the recipe.
1 cup sugar
1/2 cup vegetable oil
1 cup mashed ripe banana (about 2 bananas)
1/2 cup sour cream (or buttermilk, or milk mixed with lemon juice, as I did this time)
1 teaspoon vanilla
1 1/2 cups flour
1 teaspoon baking soda
1/2 teaspoon salt
Preheat oven to 350F/175C. Grease and flour only the bottom of a 9×5 inch loaf pan (or line cupcake pans with paper liners, if you want to make cupcakes).
In one bowl, peel and mash bananas and set aside. In another bowl, mix together dry ingredients (flour, soda, salt).
Beat sugar and oil together. Add eggs, then mashed bananas, sour cream and vanilla. Blend well. Add the bowl of dry ingredients until just moistened. Pour batter into prepared pan.
If baking loaves, bake for 50 to 60 minutes until toothpick inserted in center comes out clean. If making cupcakes, check on them after about 15 minutes. Cool 5 minutes. Remove from pan. Cool.