Season the chicken breasts with salt, pepper, garlic powder, and dried parsley.
In a large skillet with lid, melt the butter over medium-high heat. Cook the chicken until browned on both sides, about 2 minutes per side, then transfer to a plate.
Add the rice to the pan and stir for 1 minute to toast lightly. Increase heat to high, add chicken broth, lemon zest, and lemon juice, scraping the browned bits from the pan. Bring to a boil, then reduce to a low simmer and cover.
After 10 minutes, remove the lid and return the chicken to the pan. Add broccoli florets and lemon slices. Cover and cook for another 10 minutes until chicken is cooked through and rice and broccoli are tender.
Sprinkle with parmesan cheese and serve.
Notes
For extra flavor, add a pinch of red pepper flakes or fresh herbs like thyme.