Heat oil in a large skillet over medium-high heat until it shimmers. Add onion; cook until slightly softens, about 5 minutes. Add tortilla chips, then add eggs; stir until almost set, 3 to 4 minutes. Add salsa and black beans; stir until combined and heated through, about 5 minutes.
Top chilaquiles with avocado, queso fresco, red onion, and cilantro; serve immediately.
