Make cake according to directions. Let cool.
While cake cools, make blueberry sauce. In a small sauce pan, add blueberries, lemon zest, lemon juice, sugar and corn starch. Bring ingredients to a boil and cook, stirring occasionally until sauce thickens. Remove from heat and let cool.
In a microwave safe dish, add lemon curd and water. Microwave for 10-12 seconds until curd is melted. Stir. Using a pastry brush, glaze top of cake with the mixture.
Using the handle of a wooden spoon, poke holes in cake. Pour blueberry sauce over cake making sure that the sauce seeps into the holes. Cover and let cake set up in refrigerator for 30 minutes.
Using a stand or hand mixer, whip heavy cream, sugar and lemon curd until stiff peaks form. Layer topping on to cake. Chill for 1 hour or until ready to serve.