Preheat oven to 425°F.

Cover a large rimmed baking sheet (large enough to contain both racks of lamb with some space to spare) in foil.

Rub garlic cloves (if using) all over lamb and place into roasting pan

Rub lamb with 1 tablespoon oil; sprinkle with half of the rosemary, then salt and pepper. Place on baking sheet.

Mix together 2 tablespoons oil, 1 1/2 teaspoons rosemary and tomatoes in large bowl. Sprinkle with salt and pepper and toss to coat; scatter around lamb.

Roast lamb and tomatoes until thermometer inserted into thickest part of lamb registers 135°F for medium-rare, about 30 minutes. Let rest 10 minutes.

While lamb is resting, transfer tomatoes to a large serving platter and place tomatoes around the edges.

Cut lamb between bones into individual chops.