16 ounces ground beef chuck (80% lean)
½ cup finely chopped onion
2 chipotle chilies in adobo sauce (seeds removed), finely chopped, with
1 tablespoon sauce (see Tip)
½ teaspoon salt
4 hamburger buns, halved horizontally ½ cup guacamole
2 cups finely shredded romaine lettuce
4 (3/8-inch-thick) tomato slices
½ cup bottled tomato salsa plus extra for accompaniment
Prepare the outdoor grill for cooking over medium-hot charcoal or moderate heat for gas (if using).
Mix together the beef, onion, chilies with sauce, and salt in a medium bowl.
Form into 4 (4 ½-inch) patties (¾-inch-thick) with your hands.
Grill the burgers on a lightly oiled grill rack, for 4 minutes, turning once, for medium-rare.
Or cook for longer, if desired.
Meanwhile, toast the buns.
To assemble each burger, spread 2 tablespoons salsa on the cut side of the bun bottom.
Top with a cooked patty, tomato slice, and ½ cup lettuce.
Spread the cut side of the bun top with 2 tablespoons guacamole.
Add to the burgers, spread-side down.