In a small saucepan, combine the blueberries with a splash of water. Cook over medium heat, stirring occasionally, until the blueberries have softened and released their juices, about 5-7 minutes.
Use a blender or food processor to puree the cooked blueberries until smooth. Strain through a fine mesh sieve to remove the skins, if desired. Let the puree cool to room temperature before using.
Mix the Cream Cheese and Butter:
In a large mixing bowl, beat the softened cream cheese and butter together with an electric mixer on medium speed until smooth and creamy, about 2-3 minutes.
Add the Blueberry Puree:
Mix in the cooled blueberry puree and vanilla extract (and lemon zest, if using) until evenly distributed. The mixture should be uniform in color.
Incorporate the Powdered Sugar:
Gradually add the sifted powdered sugar to the mixture, beating on low speed until combined. Once all the sugar is incorporated, increase the speed to medium and beat until the frosting is smooth and fluffy. Adjust the consistency with a little more powdered sugar or blueberry puree if needed.
Chill Before Using:
If the frosting is too soft to use immediately, chill it in the refrigerator for about 30 minutes to firm up. This will make it easier to spread or pipe.
Use the Frosting:
Use the blueberry cream cheese frosting to frost your favorite cakes, cupcakes, or other desserts. It pairs particularly well with lemon cakes, vanilla cupcakes, or even chocolate desserts for a unique flavor combination.
