In a large skillet, heat the olive oil over medium-high heat. Season the chicken breasts generously with salt and pepper. Once the oil is hot, carefully add the chicken to the skillet. Cook for about 6-7 minutes on each side, or until golden brown and the internal temperature reaches 165°F (75°C). After cooking, transfer the chicken to a plate and cover it lightly with foil to keep warm.
In the same skillet, add the finely chopped onion. Sauté for approximately 3-4 minutes, stirring frequently, until the onion becomes translucent and softened. Next, add the minced garlic and cook for an additional minute, stirring until fragrant.
Stir in the drained diced tomatoes, along with the dried basil and Italian seasoning. Allow the mixture to come to a simmer, cooking for about 2-3 minutes to let the flavors meld together.
Reduce the heat to low and gradually stir in the heavy cream. Mix continuously until the sauce is well combined. Allow it to simmer gently for another 3-4 minutes, letting it thicken slightly.
Toss the fresh spinach into the skillet, stirring until it wilts down into the creamy sauce. This should take just a couple of minutes.
Return the cooked chicken breasts to the skillet, carefully nestling them amidst the creamy tomato-spinach sauce. Let everything cook together for an additional 2-3 minutes to ensure the chicken is heated through.
Taste the sauce and adjust the seasoning by adding more salt and freshly ground black pepper if needed.
Notes
Serve with crusty bread or over pasta for a hearty meal.