Tangy Tomato and Mango Salad

medium tomatoes (3 pounds), sliced 1/4 inch thick

large, ripe mangoes—peeled, pitted and sliced 1/4 inch thick

plus 1 tablespoon red wine vinegar

extra-virgin olive oil

Salt

large shallots, thinly sliced (1 cup)

thinly sliced basil leaves