Lemon Blueberry Cake

centers are springy to the touch.
For the Reduction
Put ½ cup of blueberries in the freezer.
In a small saucepan over mediumlow heat combine 1 cup blueberries 1 tbsp lemon juice 1 tbsp water and 1 tbsp granulated sugar. Mash and stir for a minute then reduce to a simmer. Simmer until reduced by half then strain into a small bowl to chill.
For the Lemon Buttercream
Cream the butter in a stand mixer then sift In the confectioners sugar in a few batches Scrape the bowl down and mix once more until lighter in color and homogenous.
Add lemon juice a tbsp at a time until a desired consistency and taste is reached.
Transfer about 1234 cup to a small bowl and mix in blueberry reduction a tablespoon at a time and mix or until you reach a desired flavor.
Transfer blueberry buttercream and around the same amount of lemon vanilla buttercream to piping bags. Snip off the tips of both. Add both bags to one piping bag and snip off the tip.
Transfer the rest of the lemon buttercream to a piping bag.
For the Assembly
Pipe blueberryvanilla buttercream between each layer. Add a thick ting of lemon buttercream to the edge
Pipe the plain lemon around the sides and smooth for a naked crumb coat. Scrape the sides and smooth cake for a naked look. 
Using an large closed star 846 tip pipe a circle of dollops about 1 inch from the edge of the cake.
Add frozen blueberries to the inside of the circle.