Ingredients:
3 tablespoons olive oil, plus more for drizzling
Four 6-to-8-ounce fillets lake or rainbow trout, sole, or tilapia, skin-on
3 tablespoons butter, cut into 1/2-inch cubes
Kernels cut from 1 ear sweet corn or 1 cup frozen corn
1/2 cup green grapes, halved
1 shallot, minced
Salt and pepper
1/2 cup dry white wine
1/4 cup chopped fresh tarragon, plus 1 tablespoon for sprinkling
Juice of 1/2 lemon
1 ripe red tomato, cut into 1/8-inch-thick rounds
2 cups watercress sprigs