Make this fresh salsa ahead so the flavors have time to blend.
Core the tomatoes. Place in one side of a 15x10x1-inch baking pan. Halve the jalapeno peppers. Remove stems and seeds. Place, cut side down, in the other side of baking pan with tomatoes. Peel away outer skin from garlic. Cut off the pointed top portion with a knife, leaving the bulb intact but exposing the individual cloves. Add to pan. Roast, uncovered, in a 450 degree F oven for 25 minutes or until tomatoes are soft and pepper skins are charred. Cool.
Remove tomato skins. Press to remove garlic paste from individual cloves of garlic. Place garlic, jalapeno peppers, and salt in a food processor bowl or blender container. Cover and process or blend with a few pulses until finely chopped. Add half of the tomatoes; cover and process or blend with a few pulses until coarsely chopped. Transfer to a large mixing bowl. Add remaining tomatoes to food processor bowl or blender container; cover and process or blend with a few pulses until coarsely chopped. Stir into tomato mixture in bowl.
Stir onions, cilantro, and vinegar into tomato mixture until combined. Cover and chill several hours to blend flavors. Serve with tortilla chips. Makes about 4 cups.