IngredientsDairy & fatEasy to get wrong
Buttermilchbuttermilk
The liquid left over from churning butter. Low in fat, mildly sour, a little thicker than milk.
The acid keeps batters tender: pancakes, waffles, plain cakes and some breads depend on it. Cold, it is also a drink on its own.
Die Verwechslungthe mix-up
The mercado sells suero de leche. That is whey, the clear liquid left from making cheese, and it is not the same thing.
Whey is thin and tastes flat. A batter made with it gets neither the acidity nor the body that buttermilk brings.
Ersatzwhat to use
Stir one tablespoon of lime juice into 250 ml of milk and leave it ten minutes. It curdles slightly, which is correct.
That is enough for any batter. As a drink it is not worth much.
Kaufenwhere
Real buttermilk is hard to find in Nayarit. What the mercado carries is suero de leche, see above.
Milk and limes are in every shop, and that settles it.