Molcajete

1 1/2 pounds plum tomatoes, unpeeled
1/2 medium onion, chunked
1/4 cup chopped fresh cilantro leaves
2 to 3 fresh jalapeños or canned
    chipotles in adobo sauce
2 garlic cloves
1 1/2 teaspoons salt
2 to 3 tablespoons cider vinegar
Pinch of sugar (optional)

Place tomatoes on a broiler pan covered with foil for easy cleaning. Broil tomatoes for 15 to 18 minutes, turning occasionally, until the tomatoes are soft and the skins split and turn dark in spots. Cool the tomatoes briefly.

In a blender, purée the tomatoes and their skins and cores with the remaining ingredients. Serve the salsa warm or refrigerate for later use.

For a chunkier salsa, leave one tomato unbroiled, chop it, and stir it and the onion, chopped rather than chunked, at the end.