Season the chicken breasts with salt and black pepper on both sides.

Heat olive oil in a large skillet over medium-high heat. Add the chicken breasts and cook for about 5-6 minutes per side until they are golden brown and cooked through. Remove the chicken from the skillet and set aside.

In the same skillet, melt the butter over medium heat. Add the chopped onion and garlic, sauté until the onion is translucent and fragrant.

Pour in the chicken broth, scraping the bottom of the skillet to deglaze and pick up any browned bits. Let the broth simmer for a couple of minutes to reduce slightly.

Lower the heat and stir in the heavy cream, grated Parmesan cheese, Italian seasoning, and red pepper flakes. Stir continuously until the sauce becomes creamy and well combined. Simmer for 2-3 minutes to allow the flavors to meld.

Add the halved cherry tomatoes to the sauce, and let them simmer for an additional 2-3 minutes until they slightly soften.

Return the cooked chicken breasts to the skillet, nestling them into the sauce. Simmer for another 2-3 minutes to let the chicken absorb some of the creamy goodness.

Taste the sauce and adjust the seasoning with salt and pepper if needed.

Garnish with chopped fresh parsley for a pop of color and added freshness.