Grilled Chicken with Pesto & Marinated Tomatoes

Chicken breast, large skinless boneless halves

Basil, fresh

Garlic

Plum tomatoes, ripe

Basil pesto, homemade or store-bought

generous tsp Dijon mustard

Lemon juice, fresh

Kosher salt and freshly ground black pepper

Olive oil, extra-virgin

Red-wine vinegar