Preheat oven to 450 degrees.
Heat the oil in an ovenproof skillet over medium heat. Add the onion, garlic, cumin and salt. Sauté until softened, about 5 minutes.
Add the salsa, sour cream and 1/4 C water to the onion mixture and stir to combine.
Fold in the tortillas, chicken and black beans. Bring the mixture to a simmer and cook for 5 - 7 minutes until warmed through.
Sprinkle with the shredded cheese and bake until the cheese is melted and bubbly, about 10 - 12 minutes.
Garnish with sliced jalapeños and serve immediately.
This is my slightly adapted version of the Cheesy Chicken Enchilada Skillet recipe from Epicurious, April 2017.