Chicken Enchiladas

Name: Chicken Enchiladas
Prep time: 20 min
Cook time: 25 min
Total time: 45 min
Cuisine: Mexican
Ingredients: 2 tablespoons vegetable oil; 1 small yellow onion, peeled and diced; 2 chicken breasts (1 lb.), boneless and skinless, diced into 1/2-inch cubes; 2 medium jalapeño peppers, finely chopped; 1/2 teaspoon salt (or to taste); 1/4 teaspoon ground black pepper (or to taste); 1 cup red enchilada sauce (homemade or store-bought), divided; 8 medium flour tortillas; 2 + 1/2 cups cheese (Mexican blend, cheddar, mozzarella or Monterey Jack cheese), shredded; fresh cilantro, finely chopped (for serving); sour cream (for serving)