Preparation Steps

• Preheat oven to 350°F (176°C) and prepare a 9x13-inch cake pan with non-stick baking spray.
• Add the dry cake mix and lemon zest to a large mixer bowl and whisk to combine.
• Add the additional ingredients listed on the box and follow package instructions for mixing and bake time.
• While the cake is baking, add the blueberries, sugar, and water to a food processor and puree until smooth.
• Pour the puree through a fine mesh sieve to remove blueberry skin bits (optional, but recommended for smoother texture).
• Combine the puree with the lemon juice and sweetened condensed milk.
• When the cake comes out of the oven, poke holes all over the cake with a straw, the end of a wooden spoon, or something similar.
• Pour the puree mixture over the top of the cake and let it soak into the cake and holes.
• Refrigerate the cake while it cools and soaks up the moisture.
• To make the frosting, combine the butter and shortening with a mixer until smooth.
• Add about half of the powdered sugar and mix until smooth and well combined.
• Add the vanilla extract and lemon juice and mix until combined.
• Add the remaining powdered sugar and mix until smooth.
• Spread the frosting evenly over the cooled cake, then top with lemon slices, zest, and blueberries, if desired.
• Refrigerate cake until ready to serve. Cake is best well covered for 2-3 days.