Combine the tomatoes, diced onion, garlic, pepper, salt, cilantro, vinegar or lime juice and jalapeño, if using.
1 15 ounce can fire-roasted tomatoes¼ cup diced onion3 cloves garlic¼ teaspoon cayenne pepper or crushed red pepper½ teaspoon salt1 tablespoon white wine vinegar3 avocados, halved1 lime, cut into wedgesCombine the tomatoes, diced onion, garlic, pepper, salt, cilantro, vinegar or lime juice and jalapeño, if using. Pulse in a food processor or blender until the salsa is chopped and blended to preference. Remove the pit of each avocado by cutting into the pit with a large sharp knife and turning the knife counter-clockwise.
Once the knife is properly wedged into the avocado pit, it should be easy to remove the pit from the flesh of the avocado, as you twist and remove the knife. Place each prepared avocado half, flesh side down, over the hot grill. Cook for about 5-7 minutes, or until grill marks appear and the avocado is warm, but not overly mushy.