Salmon with Leek and Rice Stuffing

Name: Salmon with Leek and Rice Stuffing
Ingredients: 3/4 cup plus 2 Tbs. reduced-sodium chicken stock; 2 Tbs. fresh lemon juice; 1/2 cup medium-grain or long-grain white rice; 2 Tbs. unsalted butter; 1 leek, white portion only, coarsely chopped; 1/4 cup chopped fresh flat-leaf parsley; 2 Tbs. chopped fresh chives; 1 Tbs. chopped fresh tarragon; Grated zest of 1 lemon; Kosher salt and freshly ground pepper, to taste; 1 center-cut piece salmon of uniform thickness, about 3 lb.; Extra-virgin olive oil for coating salmon; 1 large yellow onion; 1 large lemon; 3 or 4 fresh tarragon sprigs; 1/2 cup dry white wine