1. Mash avocado, lime juice, lime zest, and half of the salt and pepper in a bowl; set aside.
2. Mash beans, Tabasco, and remaining salt and pepper in another bowl.
3. Place black bean mixture on the bottom of a 4-cup crock or glass bowl. Layer avocado mash on top of beans, then sprinkle with 1/4 cup of the red onion. Top with salsa, then with sour cream. Top with chopped tomato, scallions, and remaining red onion.
4. Serve dip with tortilla chips.