In a large bowl, combine the chicken thighs with paprika, cumin, salt, black pepper, and cayenne pepper (if using). Mix well to coat the chicken evenly. Let it marinate for at least 30 minutes, or up to 2 hours in the refrigerator for more flavor.
In a large skillet, heat the olive oil over medium heat. Add the chopped onion and sauté until translucent, about 5 minutes.
Stir in the minced garlic and cook for an additional minute until fragrant.
Add the marinated chicken thighs to the skillet and brown on both sides, about 5 minutes per side.
Pour in the coconut milk and chicken broth, then add the sliced red bell pepper. Bring to a gentle simmer.
Cover the skillet and let it cook for 20-25 minutes, or until the chicken is cooked through and tender.
Stir in the lime juice and adjust seasoning if necessary.
Serve hot, garnished with fresh cilantro over rice or quinoa.