Preheat oven to 350 degrees F. Grease a 13x9-inch baking pan.
In a large bowl combine the first six ingredients (through almond extract). Beat with a mixer on low just until combined. Beat on medium 2 minutes, scraping bowl occasionally. Spread batter into the prepared baking pan.
Bake 25 to 30 minutes or until a toothpick comes out clean. Cool cake 5 minutes. Meanwhile, prepare Blueberry Sauce.
Using the handle of a wooden spoon, poke holes through cake about 1 inch apart. Drizzle lemonade concentrate over top of cake, brushing evenly. Spread Blueberry Sauce over cake. Cool completely.
In a large bowl stir a small amount of the whipped topping into the lemon curd to lighten. Fold in the remaining whipped topping. Spread over cake. If desired, top each serving with a lemon slice. Cover and store leftovers in the refrigerator up to 24 hours.
In a medium saucepan combine sugar and cornstarch. Add water; mix well. Add blueberries. Cook and stir over medium heat until mixture is slightly thickened and bubbly. Cook and stir 2 minutes more. Mash with a potato masher (mixture will not be completely smooth).