Prep for success: Zest the lemon first, then juice it. Measure out about 3 to 4 tablespoons of lemon juice. Mince the garlic and have everything ready next to the stove so the sauce comes together quickly without overcooking the garlic.
Season the chicken: Pat chicken dry with paper towels so it sears instead of steaming. Season both sides with salt, pepper, and garlic powder. If breasts are very thick, pound to an even thickness (about 3/4-inch) so they cook evenly and stay juicy.
Sear for flavor: Heat olive oil in a large skillet over medium heat. When the oil shimmers, add chicken in a single layer. Sear 4 to 5 minutes on the first side until golden brown. Flip and sear 3 to 4 minutes on the second side. The chicken does not need to be fully cooked yet. Remove to a plate and keep nearby.
Sauté the garlic gently: Reduce heat to medium-low. Add minced garlic to the same skillet and stir for about 20 to 30 seconds until fragrant. Do not let it brown, as browned garlic can taste bitter in a lemon cream sauce.
Deglaze the pan: Pour in the chicken broth and immediately scrape up the browned bits from the bottom of the skillet with a wooden spoon. Those bits add deep savory flavor to the sauce. Simmer 1 to 2 minutes to reduce slightly.
Build the creamy base: Lower the heat to low. Stir in the heavy cream and Italian seasoning. Let the mixture warm gently for 1 to 2 minutes. Avoid boiling at this stage to keep the sauce smooth.
Add Parmesan the right way: Sprinkle in the Parmesan a little at a time while stirring constantly. This helps it melt smoothly and prevents clumping. Continue stirring until the sauce looks silky and slightly thickened, about 2 to 3 minutes.
Bring in the lemon: Stir in the lemon zest first, then add 3 tablespoons of lemon juice. Simmer gently for 1 minute. Taste the sauce. If you want it brighter, add the remaining lemon juice 1 teaspoon at a time. Lemon intensity can vary by fruit, so tasting is key.
Finish cooking the chicken: Return the chicken (and any juices on the plate) to the skillet. Spoon sauce over the top. Cover and simmer on low for 6 to 10 minutes, depending on thickness, until chicken reaches 165°F (74°C). Keep the heat gentle so the cream sauce stays smooth.
Thicken and adjust: If you want a thicker sauce, uncover for the last 2 to 3 minutes and simmer gently. If the sauce gets too thick, stir in a splash of broth or cream. Taste and adjust salt and pepper. For extra lemon pop, add a pinch more zest right before serving.
Rest and serve: Remove from heat and let the chicken rest in the skillet for 2 minutes. Garnish with chopped parsley. Serve over pasta, rice, mashed potatoes, or with roasted vegetables. Spoon plenty of creamy lemon sauce over everything.