Salsa Roja

Instructions

1. Set a dry comal or heavy cast-iron frying pan over medium-high heat with no oil. When it is hot enough that a drop of water skitters, lay on 250 g of whole tomatoes and roast for 8-10 minutes, turning every couple of minutes with tongs, until the skins blister, split and blacken in patches and the flesh feels soft. Move to a plate and keep any juices.
2. On the same comal, roast 2 serrano chillies and 1 clove unpeeled garlic clove for 3-4 minutes, rolling them so they char evenly. The chillies should be blistered and softened, the garlic browned in spots and yielding when pressed. Slip the garlic out of its skin; leave the chilli skins on for smokiness.
3. Put the peeled garlic and 0.5 tsp of salt in a molcajete and crush to a smooth paste, the salt gives the stone something to bite on. Add the roasted chillies and grind them into the paste until no large pieces remain.