Step 1 / 6

dry comal or cast iron, medium-high, no oil

tomatoes + onion slices + jalapeños + unpeeled garlic, turning every few minutes until the tomato skins split and blacken in patches and the garlic gives under a thumb. No oil and no crowding: the pan has to stay hot enough to drive water off the skin, because until the surface is dry it steams rather than browns and you get pink raw-tasting salsa. Pull the garlic first — bare cloves scorch in a minute and turn acrid.