1 large onion
1 (14 oz.) prebaked Italian bread shell crust
1 can (16 oz.) refried beans
2 cups (8 oz.) shredded Cheddar cheese
3 cups shredded lettuce
1 cup (4 oz.) Mexican blend cheese
3/4 cup chopped seeded tomato(es)
1/2 cup coarsely chopped ranch-flavored tortilla chips
2 Tbsp. sliced ripe olives