Preheat the oven to 400°F (200°C).
Heat a small skillet over medium heat and sauté the diced bell peppers for 3 to 4 minutes until slightly softened. Let them cool.
In a mixing bowl, combine the sautéed bell peppers, cream cheese, mozzarella, Parmesan, minced garlic, parsley, and lemon juice until well mixed.
Cut a deep pocket into the side of each chicken breast without slicing all the way through.
Stuff each chicken breast with the pepper mixture and secure the opening with toothpicks or kitchen twine.
Season both sides with garlic powder, onion powder, Italian seasoning, paprika, salt, and black pepper.
Heat the olive oil in a large oven-safe skillet over medium-high heat.
Sear the stuffed chicken breasts for 3 to 4 minutes per side until golden brown.
Transfer the skillet to the oven and bake for 15 to 18 minutes, or until the chicken reaches an internal temperature of 165°F (74°C).
Remove the chicken from the oven and let it rest for 5 minutes before removing the toothpicks or twine.
Slice if desired and serve warm.