How to Make It
Heat oil in a large skillet over medium-high. Add onion, tomatillos, serrano, and garlic. Cook, stirring often, 5 minutes.
Stir in chicken, bell pepper, salt, cumin, and chile powder. Cook, stirring often, until bell pepper has softened and the chicken is warmed through, 5 minutes. Stir in lime juice. Serve in tortillas with toppings.