How to Make It
Preheat grill to medium-high (about 450°F).
Combine oil, rosemary, and garlic in a bowl. Rub mixture over lamb. Place lamb on oiled grate; cover and grill until a meat thermometer registers 140°F (for medium-rare), 20 to 30 minutes, turning occasionally to brown all sides. Sprinkle with salt and pepper. Slice lamb racks between ribs. Combine yogurt and ½ cup of the tomatoes; serve sauce with lamb. Top lamb pieces with remaining ¼ cup chopped tomatoes.