Cook the pasta in well-salted water until al dente. Drain, rinse under cool water, and set aside to cool completely.
In a skillet, brown the ground beef over medium heat. Drain excess fat, then stir in taco seasoning and a splash of water.
Simmer 1–2 minutes until coated. Cool to room temperature.
Make the dressing: whisk sour cream, mayonnaise, salsa, lime juice, olive oil, a pinch of salt, and pepper. Taste and adjust acidity or heat as needed.
In a large bowl, combine cooled pasta, seasoned beef, black beans, corn, tomatoes, bell pepper, red onion, and cheese.
Pour in most of the dressing and toss until everything is lightly coated.
Add more dressing if needed; you want it creamy but not heavy.
Fold in lettuce and cilantro just before serving so they stay crisp.
Top with diced avocado and a handful of crushed tortilla chips. Serve with lime wedges and extra salsa on the side.