Fill the bottom of the ramekins with half of the sliced tortillas. Layer over them half of the chicken, bell pepper, and jalapeño. Pour ¼ cup of the sauce into each of the ramekins, then sprinkle with 1 cup of the cheese.
Repeat by layering the remaining tortillas, chicken, bell pepper, jalapeño, and cheese, and top off with the remaining sauce.
Place the ramekins on a large baking sheet and transfer to the oven.
Bake, uncovered, until the cheese is bubbly and lightly browned, 18 to 20 minutes.
Let the casseroles cool for 8 to 10 minutes before sprinkling with the cilantro and serving warm.