Heat a large OVENPROOF skillet or cast iron skillet coated in cooking spray and 1/2 tablespoon of olive oil over medium-high heat. Combine the fennel seeds, garlic powder, oregano, and sea salt & freshly cracked pepper, to taste in a small dish and mix well. Sprinkle spice rub evenly over both sides of the chicken.
Add chicken to the hot skillet and cook for 3 minutes or until browned. Turn chicken over; then place into the oven for 20 minutes, or until the chicken has cooked through. Remove the chicken to a serving plate and cover with a tin foil tent.
Add the remaining olive oil over medium-high heat in the same skillet. Add bell peppers and onion; sauté for 3 minutes. Stir in broth, scraping pan to loosen browned bits. Reduce heat; simmer for 5 minutes.
Increase heat to medium-high. Stir in vinegar then season with sea salt and freshly cracked pepper, to taste; cook 3 minutes, stirring frequently. Serve bell pepper mixture and sauce over chicken. Enjoy!