Buttermilk
Buttermilk is a cooking liquid or sauce that can change flavor, body, or acidity quickly. Add it gradually, then simmer, reduce, or finish gently to match the dish.
Identity
Cooking liquid
Add gradually and taste as you go.
Liquids can change seasoning, acidity, aroma, and body quickly. Add them in stages when balance matters, then simmer, reduce, or finish gently to match the dish.
Wikimedia Commons
Reference image
Buttermilk reference image.

Source: Wikimedia Commons
Used In Recipes
Substitutions
Acceptable
Buttermilk -> Plain Greek Yogurt
1 cup (227g) buttermilk or plain Greek yogurt*
The source lists this as an alternative in the same ingredient row.
Source: Cinnamon-Crisp Coffee Cake
Acceptable
Buttermilk -> Yogurt
1 cup (227g) buttermilk or yogurt, at room temperature
The source lists this as an alternative in the same ingredient row.