Place tomatoes and chiles in a pan, cover with water, and bring to a simmer.

Cook at a fast simmer until tomatoes are fairly soft, about 5 minutes.

Set aside.

Roughly chop chiles.

Combine garlic, chopped chiles, and 1/3 cup of cooking water in a blender.

Blend until well broken, about 5 seconds.

Add unpeeled, strained tomatoes and blend for a few seconds; sauce should have a rough texture.

Heat oil in a frying pan or cazuela.

Add sauce and cook over high heat, stirring occasionally and scraping the bottom, until reduced and the raw taste of garlic has disappeared, about 6 minutes.

Add salt to taste.