Heat a skillet on medium heat and melt 1 tablespoon of butter in it.
Season the chicken breasts with oregano, salt, and pepper.
4 chicken breasts, 1/2 teaspoon salt, 1/4 teaspoon pepper, 1 teaspoon oregano
When the skillet is hot, place the seasoned chicken breasts in it and cook for 5-7 minutes on each side until they're cooked through. Remove from the pan.
Turn the temperature down to medium-low and add the rest of the butter to the skillet. Use a spatula to loosen any bits of stuck on chicken.
Add the chopped onion and cook for a few minutes until it becomes translucent.
1/2 onion
Add the minced garlic and cook for an additional 30 seconds.
4 garlic cloves
Place the tomato slices in the skillet and cook until the skins begin peeling off, about 5-8 minutes.
4 roma tomatoes
Add the baby spinach and cook it until it wilts, about 2 minutes.
3 cups baby spinach
Whisk in the heavy cream and cheese.
1 1/2 cups heavy cream, 1/3 cup parmesan cheese
Bring the sauce to a slow simmer, and let it cook for about 5 minutes until it's slightly reduced. Make sure to whisk frequently to prevent burning.
Add the chopped basil and chicken to the skillet, and let the sauce continue to simmer until the chicken is heated through.
1 tablespoon fresh basil
Serve immediately with fresh lemon wedges as garnish.
4 lemon wedges