Heat olive oil in a large skillet over medium-high heat.
Season chicken with lemon pepper. Add chicken to skillet and cook 4–5 minutes per side or until cooked through. Remove chicken and set aside.
Add onion to skillet and cook for about 3 minutes until soft. Add garlic and cook 1 minute more. Pour in chicken broth and deglaze pan, scraping up any browned bits from the bottom of the skillet.
Slowly stir in heavy cream and bring to a simmer. Add Parmesan and stir until melted. Add the sun-dried tomatoes, Italian seasoning, garlic powder, and spinach. Cook and stir until spinach is wilted. Season to taste with salt and pepper.
Add the chicken back to the pan. Cook for 5 minutes or until warmed through.