Lemon Pudding Cake

Name: Lemon Pudding Cake
Yield: Makes 6 Servings
Ingredients: Whipped cream, for serving (optional); Milk, 1¼ cups (10 fl oz/310 ml); Cream of tartar, ¼ teaspoon; Sugar, 1 cup (8 oz/245 g); Flour, ¼ cup (1½ oz/45 g); Lemon zest, 2 teaspoons finely grated; Salt, ⅛ teaspoon; Unsalted butter, 4 tablespoons (2 oz/60 g), melted; Eggs, 3, separated; Lemon juice, ⅓ cup (3 fl oz/80 ml)