Heirloom Raw Tomato Salad

2 tablespoons extra-virgin olive oil 1 tablespoon malt vinegar 2 small heirloom raw  tomatoes (about 8 ounces total), cored, cut into thin wedges 1 cup (packed) small watercress sprigs 1/4 cup chopped fresh chervil or 2 tablespoons chopped fresh parsley   Preparation...