It's worth making your own fresh salsa. This particular recipe comes from the cousin of one of our restaurant chefs, who found an easy way to char and blend delicious Mexican ingredients to make a fresh effortless, rustic salsa. (Note: Total time includes time to heat up the grill)
Heat a gas grill on medium-high or light a charcoal grill. Cut the onion into ½-inch slices, keeping them intact. Gather together the tomatoes, green chiles, garlic cloves, and onion slices and lay everything on the hot grill. Cook the vegetables, turning occasionally, until everything is well-charred and softened, about 10 minutes for the chiles, 15 minutes for the garlic, and 20 minutes for the tomatoes and onions. Transfer to a plate and let cool.
When vegetables are cool enough to handle, peel the garlic. De-stem and coarsely chop the jalapeños. In a food processor, combine the garlic and chiles and pulse until coarsely chopped. Add the tomatoes and pulse until roughly chopped; transfer to a serving bowl and season with about ¾ teaspoon of salt. Coarsely chop the charred onion by hand and stir into the tomato mixture, along with about 2 tablespoons of water to give the salsa an easily spoonable consistency. Taste, and add salt if necessary before serving.