Preheat your oven to 350°F (175°C). Grease and line three 8-inch round cake pans with parchment paper.

In a large mixing bowl, beat the butter until creamy. Gradually add the sugar, beating until light and fluffy. Add the eggs one by one, mixing in the vanilla extract.

In a separate bowl, whisk together flour, baking powder, and salt. Alternately add this dry mix and buttermilk to the butter mixture, mixing well. Fold in the lemon zest, juice, and blueberries.

Divide the batter among the prepared pans, smooth the tops, and bake for 21 to 25 minutes until golden.

Allow the cakes to cool in the pans for 10 minutes before transferring them to a wire rack to cool completely.

Beat together cream cheese and butter until smooth. Gradually mix in sugar, milk, lemon extract, and sea salt until desired consistency is achieved.

Trim the tops of the cooled cake layers. Spread frosting between layers and on top and sides of the cake.

Garnish with fresh blueberries and lemon slices. Chill for at least 2 hours before serving.