Use a meat mallet to pound the chicken breasts to an even thickness. Season both sides of the chicken with Cajun seasoning, making sure to coat them well.
In a large skillet over medium-high heat, add olive oil. Allow it to heat until shimmering, but not smoking.
Place the chicken in the skillet and cook for about 5-6 minutes on each side, or until golden brown and cooked through (internal temperature should reach 165°F or 75°C). Remove the chicken from the skillet and set aside.
In the same skillet, add sliced bell peppers and onion. Sauté for about 5-7 minutes until the vegetables are tender and slightly caramelized.
Stir in the minced garlic and drained diced tomatoes. Cook for an additional 2-3 minutes until fragrant.
Return the chicken to the skillet, nestling it into the vegetable mixture. Sprinkle oregano over the top, and season with salt and pepper to taste. Let it simmer for an additional 5 minutes, allowing the flavors to meld together.
Remove from heat, garnish with freshly chopped parsley, and serve hot.
Notes
Ensure chicken is cooked to an internal temperature of 165°F (75°C).