Preheat the oven to 375°F (190°C).
In a large skillet, heat olive oil over medium-high heat.
Add the chicken pieces to the skillet and cook for 5-6 minutes until lightly browned but not fully cooked through. Remove chicken from skillet and set aside.
In the same skillet, add the sliced red, green, and yellow bell peppers, and onion. Sauté for 5 minutes until vegetables are slightly softened.
Add the minced garlic, chili powder, ground cumin, smoked paprika, dried oregano, salt, black pepper, and crushed red pepper flakes to the vegetables. Stir well and cook for 1 minute until fragrant.
Return the chicken to the skillet and add the diced tomatoes and chicken broth. Stir to combine all ingredients.
Allow the mixture to simmer for 3-4 minutes to meld flavors and slightly reduce the liquid.
Transfer the chicken and vegetable mixture into a 9×9 inch casserole dish, spreading evenly.
Sprinkle the reduced-fat shredded cheddar cheese evenly over the top.
Bake uncovered in the preheated oven for 15-20 minutes until the cheese is melted and bubbly and the chicken is fully cooked (internal temperature should reach 165°F or 74°C).
Remove from oven and let the casserole rest for 5 minutes.
Garnish with chopped fresh cilantro before serving.