Two different fruits, one job
Many Mexican sauces are built on either tomatillos or tomatoes. They look alike at a glance, and both are commonly charred or simmered and blended with onion, garlic and chile. But they are different plants, and the sauces they make taste and behave differently.
Both belong to the nightshade family and have deep roots in Mesoamerica. Origins and early domestication of each are studied and sometimes debated, so it is safest to say that people in the region have grown and eaten both for a very long time.
What a tomatillo is
The tomatillo, Physalis philadelphica, is a small round fruit wrapped in a papery husk, similar to a Chinese lantern. It is usually harvested green, though some ripen to yellow or purple. The husk is removed before cooking, and the fruit underneath is firm and coated with a sticky film.
The tomatillo is sometimes called a green tomato, but that is a mistake. An unripe green tomato is a different thing: a tomato that has not finished ripening. Tomatillos stay tart and firm even when fully mature.
What they taste like
- Tomatillos. Bright, tart and slightly citrusy, with a vegetal edge and a hint of herbal flavor. They have a lot of acidity and less sugar, and they hold up to long simmering and charring.
- Tomatoes. Sweeter, rounder and more savory (umami-rich) when ripe, with a softer texture. They contribute body and a deeper red color to sauces.
Texture also differs. Tomatillos tend to give a sauce a slightly thick, glossy quality when blended. Tomatoes give a sauce that is more watery, or heavier if cooked down, depending on the variety and ripeness.
Preparing tomatillos
- Peel off the husks.
- Rinse the fruit under warm water, rubbing off the sticky coating. It is harmless but can taste soapy or bitter in some cases if left.
- Cook them in one of several ways: simmer in water until they turn olive green and soft, roast under a broiler or on a comal griddle until blistered and spotted, or eat raw, finely chopped or blended.
Each method changes the sauce. Simmering gives a mild, clean, bright flavor. Roasting adds smokiness and sweetness, which balances the tartness. Raw tomatillo sauce is sharpest. A traditional tomatillo salsa often combines the cooked fruit with serrano or jalapeño chile, cilantro, onion and salt. A molcajete mortar is a classic tool for grinding it.
Choose firm fruits that fill their husks and are not shriveled, and discard any that feel soft or look moldy. Stored in their husks in a paper bag in the refrigerator, they typically keep for a couple of weeks.
Preparing tomatoes
Tomatoes for Mexican sauces are often a firm, flavorful kind of plum or roma tomato. They are usually roasted or boiled whole, then peeled if desired, and blended with onion, garlic and chile. Roasting on a comal griddle until the skin blackens in places adds a smoky depth. Raw tomatoes are used in uncooked mixtures like pico de gallo, where freshness and texture matter.
When each is used
- Green sauces (salsa verde, many table salsas, green enchilada sauces, some stews such as pork in green sauce) typically start with tomatillos. Their acidity cuts through rich meats and cheese.
- Red sauces (tomato-based sauces for eggs, rice, some enchiladas) use tomatoes, often with dried chiles for color and depth. Mexican red rice relies on tomato blended with onion and garlic.
- Mixed sauces. Some recipes use both, balancing sourness with sweetness. Many moles include a small amount of tomato or tomatillo as part of a long list of ingredients.
Regional preferences vary, and a cook’s choice depends on the dish and what is in season, rather than a strict rule.
Substitutes
Substituting one for the other changes the dish, though it can work in an emergency.
- If tomatillos are unavailable, canned tomatillos are a common choice, and they work well in cooked sauces. Green tomatoes plus a squeeze of lime are sometimes suggested, but the flavor is not the same.
- If tomatoes are unavailable, canned whole tomatoes are generally a reasonable stand-in for a cooked red sauce.
Adjust salt and acidity to taste after switching.
Keeping and serving
Cooked sauces made with either fruit usually keep for a few days in a covered container in the refrigerator, and they can often be frozen. Cool them promptly after cooking. Tomatillo sauces that contain raw garlic or herbs should be eaten sooner. Reheat leftovers until steaming before serving, and discard anything that smells off.