1 turkey (10-12 lbs), thawed if previously frozen
1/2 cup (1 stick) unsalted butter, at room temperature
1/4 cup fresh parsley, chopped
1 tablespoon fresh thyme, chopped
1 tablespoon fresh rosemary, chopped
1 teaspoon fresh sage, chopped
1 1/4 teaspoons salt
1 lemon, quartered
1 small yellow onion, quartered
1/4 teaspoon plus 1/8 tsp black pepper
2 tablespoons all-purpose flour
2 cups unsalted turkey or chicken stock