Substitutes for buttermilk or homemade version of buttermilk (this is good to use when you cannot find buttermilk or it is needed in a pinch but it is hard to beat the quality and taste of real cultured buttermilk):
To make buttermilk: 1 tablespoon of lemon juice or vinegar added to 1 cup of milk and allow to sit for 10 to 15 minutes. The milk will curdle slightly, just mix and use.
Substitutes: Sour cream thinned to the consistency of buttermilk or thick milk. Or 2 tablespoons of milk with enough yogurt added to equal 1 cup. If the yogurt is very thick then 3 tablespoons plus yogurt to equal 1 cup.