sour cream
Mexican cultured cream, thinner and milder than sour cream, with a gently tangy note.
Crema is a cultured cream from Mexican cooking, runnier and slightly richer than sour cream, so it can be drizzled over tacos or enchiladas and holds up better to heat without curdling. Outside Mexican or Latin American grocers and online shops it is hard to find, while sour cream and crème fraîche are in every supermarket.
Substitute:
Crème fraîche thinned with a little milk or lime juice comes closest and also tolerates heat; sour cream is tangier and leaner and is more likely to curdle in hot sauces.