Prepare the chicken by patting it dry with paper towels and removing the giblets and/or gravy pouch.
Sprinkle chicken with salt and pepper. Place lemon and rosemary in the cavity. Tie chicken’s legs together with kitchen twine. Spread butter over the top of the skin.
Place chicken in a roasting pan or a 9-x-13-inch baking dish. Bake for 60 minutes, then check the temperature in the thickest part of the thigh. Continue cooking, checking every 10 minutes, until it reaches 165 degrees F.
Remove chicken from the oven and let it sit 10–15 minutes before cutting and serving.
Slow Cooker Directions: Spray a slow cooker with cooking spray. Roll a piece of aluminum foil into a ring and place it around the bottom of the slow cooker as a rack for the chicken. Prepare chicken as directed in Steps 2–3 above, then place it on top of the aluminum foil ring. Cover and cook on high for 3–4 hours, until a thermometer inserted in the thigh registers 165 degrees or higher. Move chicken to a sheet pan or baking dish and broil in the oven for 3–5 minutes, until the skin is browned. Let rest for 10 minutes before cutting and serving.Use It Up: Leftover chicken can be used to make White Chicken Chili, Chicken Tortilla Soup, Chicken Tacos, Chimichangas, or Flautas.