In a large skillet over medium-high heat, cook the ground beef until browned and fully cooked, breaking it up with a spoon as it cooks. Drain any excess fat.
Add the taco seasoning mix and water to the skillet. Stir to combine and cook for another 2-3 minutes, or until the sauce thickens. Remove from heat and let cool slightly.
Prepare the Salad:
In a large salad bowl, combine the chopped lettuce, black beans, corn, cherry tomatoes, shredded cheddar cheese, red onion, and black olives (if using).
Assemble the Salad:
Add the slightly cooled ground beef to the salad bowl.
Just before serving, add the crushed Doritos and diced avocado (if using).
Dress the Salad:
Pour the Catalina dressing over the salad and toss gently to combine, ensuring all ingredients are evenly coated.
Serve:
Garnish with chopped fresh cilantro if desired.
Serve immediately to maintain the crunchiness of the Doritos.