Although a lot of my favorite recipes like my Gram's Chocolate Zucchini Cake and Banana Chocolate Chip Pancakes call for buttermilk, I rarely have any on hand. Instead, I make a substitution of milk and lemon juice - here's how:
Butter Milk Substitute
1 cup milk
1 tablespoon fresh lemon juice
Combine the milk and lemon juice in a measuring cup, give it a little stir, then let it set for 5 minutes.