Arrange a rack in the center of your oven, and preheat to 425°.
Cut 1 lemon in half crosswise and remove any visible seeds.
Cut 1 head of garlic in half crosswise.
Melt ½ stick butter in a small saucepan or microwave in a small bowl.
Place 1 3–4-lb. whole chicken on a cutting board and pat it dry with paper towels.
Season every surface of chicken with lots of salt and pepper.
Transfer chicken breast side up to a large oven-safe skillet.
Arrange lemon and garlic cut sides down in skillet around chicken.
Drizzle chicken all over with melted butter and transfer to oven.
Roast until chicken is nicely browned and cooked through, checking for doneness after 45 minutes.
Let chicken rest in skillet at least 15 minutes before carving.
Transfer chicken to a platter and pour pan juices over top of the meat.
