Salsa macha is a Mexican chile oil, a spoonable condiment of dried chiles, garlic, peanuts and sesame seeds fried in oil and pulsed chunky. It comes from Veracruz, the port city on the Gulf of Mexico, where it is spooned over tacos, eggs, grilled meats and pozole. There is no tomato in it, no onion and no fresh herbs; the flavour is smoky, nutty and garlicky, with a heat you control by the chiles you choose. A spoonful of vinegar is in most recipes outside Mexico for brightness, though some Veracruz versions leave it out. It is also called macha sauce, and it belongs to the same family as Mexican chili oil, a term you will see on jar labels and menus.
The name is part of the story, and the sources disagree about it, so this page reports both readings. Most often it is explained as coming from machacar, to crush or grind, a nod to the molcajete, the basalt mortar in which the salsa was once made. Other sources, including Rick Bayless, derive it from macho, brave or strong, because the salsa was hotter than the fresh salsas around it. The jury is still out, and neither reading is presented here as proven fact.
Veracruz is the consensus home, though Oaxaca claims a version of its own, built on sesame seeds rather than peanuts. That sesame version is the one you will recognise from Oaxacan markets and from jars that list sesame first. The peanut version in this recipe is the Veracruz build, the one most top-ranking recipes follow. What the two share is the method: dried chiles and garlic fried gently in oil, never burnt, then pulsed just enough to keep the crunch.
It helps to know what salsa macha is not. It is not salsa roja, which is tomato, onion and chiles, usually fresh or cooked, and eaten the same day. It is not Chinese chili crisp, though the two are cousins. Both start from dried chiles in oil with fried garlic, but chili crisp adds onion, soy sauce, ginger, Sichuan pepper and often fermented soybeans and a little sugar, while salsa macha adds peanuts and vinegar and is usually made without sugar, smokier and nuttier. And it is not matcha. Matcha is Japanese powdered green tea; macha is Mexican chile oil. The words sound alike, the spelling differs by one letter, and the confusion is common enough that it is worth saying plainly: nobody puts matcha in their macha.
Two practical facts before you start. The whole recipe takes about 35 minutes, but only 20 of those are active work; the other 15 are cooling, and you must not blend the salsa hot. And this is a refrigerated condiment, not a shelf-stable one. Because it contains garlic in oil, keep it in a clean airtight glass jar in the fridge and use it within a week, following the food-safety guidance in the storage question below. For longer keeping, freeze it in ice-cube trays for up to three months. Never store it at room temperature, and never try to can it at home.