Start by seasoning the chicken breasts with Cajun seasoning, ensuring they are evenly coated.
In a large skillet, heat the olive oil over medium-high heat. Add the seasoned chicken breasts and cook for about 5-7 minutes on each side, or until cooked through and golden brown. Remove the chicken from the skillet and set aside.
In the same skillet, add the diced onion and sauté for about 3-4 minutes until translucent. Add the minced garlic and cook for an additional 1 minute until fragrant.
Pour in the heavy cream and chicken broth, stirring to combine. Bring the mixture to a gentle simmer.
Add the diced tomatoes and chopped spinach to the skillet, stirring until the spinach wilts. Season with salt and pepper to taste.
Return the cooked chicken to the skillet, spooning the creamy sauce over the top. Let it simmer for another 5 minutes to heat through.
Serve hot, garnished with fresh parsley.