1/4 cup dry bread crumbs
1/4 cup finely chopped onion
1 1/2 pounds lean ground beef
1 (1 1/4-ounce) package taco seasoning mix
1 (7- to 8-inch) round loaf unsliced bread, sliced in half horizontally*
Sliced pitted ripe olives
Line baking sheet with waxed paper; set aside.
Combine all burger ingredients except bread and butter in bowl; mix well. Shape into large (8- to 9-inch) patty. Place onto prepared baking sheet. Cover; refrigerate at least 30 minutes.
Heat gas grill on medium or charcoal grill until coals are ash white.
Place patty onto grill. Grill, turning once (if necessary, use two metal spatulas), 13-15 minutes or until internal temperature reaches at least 160°F and meat is no longer pink in center. Place cheese onto patty; continue grilling 2-4 minutes or until cheese is melted.
Spread bread halves with butter. Place bread halves, cut-side down, away from coals. Grill bread, rotating occasionally, 3-4 minutes or until toasted.
Place burger onto bottom half of bread; top with lettuce, tomato, olives, sour cream, guacamole, salsa and top half of bread. Cut into 6 wedges.
*If loaf of bread is too tall, slice into 3 horizontal layers. Remove center layer for other use.
If desired, jumbo burger can be made into 6 individual patties, using 6 slices cheese and served on 6 hamburger buns. Shape hamburger mixture into 6 patties. Place patties onto grill. Grill, turning once, 12-15 minutes or until internal temperature reaches at least 160°F and meat is no longer pink in center. Top each with cheese. Continue grilling until cheese is melted. Toast buns and serve as directed above.