The Best Meatloaf I've Ever Made

INGREDIENTS

• 1 tablespoon butter
• 1/4 cup minced onion
• 2 cloves garlic, minced
• 1 1/2 teaspoons salt
• 1 1/2 teaspoons freshly ground black pepper
• 2 pounds extra-lean ground beef
• 3 slices bread, toasted and crumbled
• 7 buttery round crackers, crushed
• 1 egg, lightly beaten
• 3 1/2 tablespoons sour cream
• 1 1/2 tablespoons Worcestershire sauce
• 1 (15 ounce) can tomato sauce, divided
• 1/4 cup milk (optional)
• 3 tablespoons ketchup