Preheat the oven to 350°F/177ºC. Prepare three 6-inch or two 8-inch cake pans by spraying the sides with baking spray and fitting a parchment paper circle to the bottom of each pan. Alternatively, you can grease and lightly flour the pans.

In a medium bowl, add the cake flour, baking powder, and salt and whisk to combine. Set aside.

In the bowl of your stand mixer (a handheld mixer works fine too!), beat the butter on high for two minutes until creamy. Add in the sugar and continue to cream on medium-high for another two minutes, scraping down the bowl and paddle as needed. Turn the mixer to low and add the eggs one at a time, mixing thoroughly after each addition. Add the sour cream, lemon zest, lemon extract, and vanilla extract. Turn the mixer to high and beat for 1 minute, scraping down the bowl and paddle once more.

With the mixer on low speed, add in the dry ingredients and mix until just combined. Add the milk slowly and mix until just incorporated. Scrape down the sides and bottom of the bowl and give it a few stirs to make sure there are no lumps. The batter will be slightly thick.

Divide the batter evenly between the prepared cake pans and bake for 30-35 minutes. They’re done when they spring back to the touch and a toothpick inserted into the middle comes out clean. Let the cakes cool in the pan for five minutes before turning them out onto a wire rack for an additional few hours of cooling. Make sure they’re entirely room temperature before applying any frosting.

With a food processor, grind the freeze dried blueberries into a fine powder and set aside. Whip the butter using a stand mixer with a paddle attachment on medium speed until it’s creamy and light in color, about 5 minutes. Add vanilla, milk, and blueberry powder and continue to mix on medium for 3 minutes.

Add the powdered sugar in two additions, mixing on low until fully incorporated. Add the salt and continue to mix on low for another 30 seconds.

After torting the cake layers, fill and frost them with the blueberry buttercream. To replicate the look of the cake design pictured, frost the cake with a smooth layer of blueberry buttercream, then refrigerate it for about 20 minutes to let it firm up.

Prepare two piping bags by fitting the first with Wilton Tip 1M and the second with Wilton Tip 4B, then fill both with blueberry buttercream. Pipe rosettes and stars in a diagonal design on the front of the cake, then continue the pattern partially around the top edge. Add some fresh blueberries and yellow sprinkles onto the piping wherever you desire.