Grilled Chicken with Pesto & Marinated Tomatoes

Looking for a way to dress up simple chicken breasts tonight? Here, the tomatoes and pesto pack a lot of flavor for such a simple preparation. Plus, the tomatoes do double duty: Use them as a colorful topping for hot slices of garlic toast.
Or, toss them with cooked pasta along with olives, chickpeas, and
roasted red peppers.

• 4 large skinless, boneless chicken breast halves
• 2/3 cup homemade or store-bought basil pesto
• 3 Tbs. fresh lemon juice
• 4 ripe plum tomatoes, cored
• 3 Tbs. extra-virgin olive oil; more for brushing
• 1-1/2 tsp. red-wine vinegar
• 1 clove garlic, minced
• 1 generous tsp. Dijon mustard
• 2 Tbs. chopped fresh basil (or a mix of cilantro, basil, and flat-leaf parsley)
• Kosher salt and freshly ground black pepper

Heat a gas grill to high. Butterfly the chicken breasts by making a horizontal cut through the center of the thickest long side of the breast. Cut almost but not entirely through each breast. Open the breasts like a book. Cover with plastic wrap and pound to flatten slightly to an even thickness. Combine the pesto with 2 Tbs. of the lemon juice and rub over the chicken in a nonreactive dish.

Cut each tomato in half. Gently remove the seeds with your fingers, coarsely chop the flesh, and put it in a bowl. In a small bowl, combine the oil, vinegar, garlic, mustard, basil, remaining 1 Tbs. lemon juice, 1 tsp. salt, and a generous amount of pepper. Pour this over the tomatoes and combine well. Remove the chicken from the pesto, shaking to remove excess marinade, and sprinkle lightly with salt. Grill, turning once, until golden on both sides and cooked through, 4 to 6 minutes total. Transfer the chicken to a platter and serve hot or at room temperature. At the table, spoon the tomatoes over the chicken.