Melt butter in a medium sized frying pan. Add diced onion to pan and saute until softened. Next add the basil pesto sauce and cubed chicken. Continue on medium heat just until chicken is no longer pink. Add diced red bell pepper; stir in well to coat with basil pesto sauce. Pour in Red Pepper and Tomato Soup. Add oregano and chili flakes. Simmer in sauce until chicken is cooked through. Taste sauce and add desired amount of sea salt and ground pepper.