1 small yellow onion
Extra-virgin olive oil
1 red bell pepper
1 Serrano pepper
2 Tbs. finely sliced basil
2 Tbs. red wine vinegar (such as grenache)
Prepare a moderately hot hickory fire in your grill.
Wash and core tomatoes. Peel onion and slice it in one-inch rings. (Do not separate rings.)
Coat both lightly with olive oil. Place on a clean grill rack over the moderately hot fire and close lid. Cook until tomatoes are charred on the outside and have begun to burst a little when done, about 15 minutes, and onions are caramelized on both sides and tender, about 20 minutes.
Toss peppers with olive oil to coat skins. Grill them long enough to blister the skin, about 10 minutes. Turn all vegetables over halfway through cooking. When done, place tomatoes and onion on a plate to cool. Place peppers in a bowl and cover with plastic wrap to steam.
Cut tomatoes into 1/4-inch dice. Remove outer skin of the onion and cut it in 1/4-inch dice. Wipe charred pepper skins away with a towel and discard. Pull peppers apart and discard seeds. Cut peppers into 1/4-inch dice.
Place all vegetables in a bowl. Add basil and vinegar, season to taste with salt, and mix thoroughly. Serve at room temperature as a dip or alongside roasted and grilled meats. Note: Tightly covered, the salsa can be refrigerated for up to 24 hours but should be brought back to room temperature before serving.