Preheat the oven to 350 degrees. In an ovenproof baking/serving dish combine the cheese with the salsa and bake until the cheese melts, about 10 minutes. Serve immediately.
In a cast iron skillet, over a very high heat, char the onion slices and remove. Toast the garlic and remove. Add 2 tablespoons of the olive oil to the skillet and sear the chiles until charred. Add the remaining oil, the oregano, lime juice, and salt and cook 1 minute. Place all the ingredients in a food processor fitted with a metal blade. Process until they are roughly chopped but smooth.
Recipe copyright Mary Sue Milliken and Susan Feniger, 1997, all rights reserved