1.
Place the peppers, whole tomato, and peeled onion into a saucepan and add water to cover. Sprinkle in the cumin seeds, then bring to a boil over high heat. Reduce heat to a simmer, and cook until the vegetables are tender and the skin begins to peel from the tomato, about 10 minutes.
2.
Pour off the water, and let the veggies cool on a plate. Cut the onion into quarters and place into a food processor. Remove the stems from all 4 peppers, remove the seeds if desired (see note below), and add to the food processor. Pulse until the onion has been chopped into 1/2-inch pieces.
3.
Discard the skin and seeds from the tomato, and place into the food processor along with the cilantro and lime juice. Process until the salsa is ground to your liking. Refrigerate 1 hour before serving with tortilla chips, or on top of tacos.