Perfect Roast Chicken

INGREDIENTS

• Olive oil
• 1 lemon, halved
• Kosher salt
• 1 head garlic, cut in half crosswise
• 1 (5 to 6 pound) roasting chicken
• 1 large yellow onion, thickly sliced
• 4 carrots cut into 2-inch chunks
• 1 large bunch fresh thyme, plus 20 sprigs
• 1 bulb of fennel, tops removed, and cut into wedges
• Freshly ground black pepper
• 2 tablespoons (1/4 stick) butter, melted