Preheat oven to 350 degrees. Grease three 8- to 9-inch round cake pans. Line with parchment paper rounds, then grease parchment paper.
To make the cake:
In a stand mixer, cream butter, then add sugars and beat until light and fluffy. Add eggs and vanilla and mix to combine.
In a separate bowl, combine flour, baking powder and salt; mix well. Combine buttermilk, lemon zest and lemon juice in another small bowl. Add dry ingredients to creamed mixture alternately with buttermilk-lemon mixture. Mix until just combined.
Toss blueberries with 1 tablespoon flour and gently fold into the cake batter. Batter will be very thick; do not overmix.
Spoon batter evenly into prepared cake pans. Bake for approximately 21 to 25 minutes or until a toothpick inserted into the center comes out clean. Remove from the oven and cool completely in the pan before assembling and frosting.
To make the cream cheese frosting:
Beat cream cheese and butter together on medium speed until smooth. Add powdered sugar, 1 1/2 tablespoon heavy cream, vanilla and salt. Beat again until smooth.
Add additional cream if necessary to achieve desired consistency.
If you plan on piping any decorations, you may need to add additional powdered sugar to get the proper consistency.
Assemble the cake:
Fill and frost the cooled cake layers with cream cheese frosting.
Decorate with extra blueberries, lemon slices, and fresh flowers.
Refrigerate at least 45 minutes before cutting or else cake may fall apart as you are cutting. Store leftover cake in the refrigerator.