Combine all ingredients in a double boiler and heat while stirring constantly with a whisk. It’s done when it’s thick enough to coat the back of a spoon.

Preheat oven to 350°. Line three 8 inch cake pans with parchment paper and grease sides.

Mix cake batter: Beat butter and sugar until light and fluffy – 3-4 minutes. Add vanilla, sour cream and lemon zest and mix until combined. Add egg whites in two batches, scraping down the sides of the bowl as needed. In a separate bowl combine dry ingredients. In another small bowl combine milk and water. Add half the dry ingredients to the batter and mix until combined. Add milk/water combo and mix until combined – scraping sides of bowl as needed. Add remaining dry ingredients and mix until smooth.

Divide batter evenly between the three pans and bake for 23-25 minutes, or until a toothpick comes out clean.

Make raspberry frosting: Puree fresh raspberries. Pres through a fine sieve to remove pulp and seeds. You should end up with about ½ C raspberry juice. Combine butter and shortening and beat until smooth. Add 4 cups of powdered sugar and beat until smooth.

Add raspberry juice and beat until well combined. Slowly add remaining powdered sugar, beating until smooth. Add 1-2 tablespoons of milk or water as needed to thin.

Put the cake together: Remove the top of the cakes with a large serrated knife to make them flat. Please first cake on a plate or cake circle. Top cake layer with about ¾ cup of frosting and spread evenly. Pipe a dam of frosting around the outside edge of the cake, and then fill it with half the lemon curd. Add the second layer and repeat this process. Add the final layer of cake and frost the outside of the cake.

Decorate the cake: Before the frosting on the top of the cake has a chance to firm up too much, place a design on the top. Pipe additional frosting on the cake as desired. Add lemon slices and raspberries for garnish.

Cake should be refrigerated until ready to serve. Best if served after allowing to sit out for 30 minutes.