To make sauce: In a small saucepan over medium heat, combine wine, shallot, and zest; cook until reduced by half, about 5 minutes. Whisk in half-and-half, milk, and turmeric; bring to a simmer. In a small bowl, dissolve cornstarch in water; whisk into wine mixture. Continue simmering to thicken, about 1 minute. Remove from heat and stir in lemon juice. Season with salt to taste; keep warm. (Makes 1⁄2 cup.)