To make the cake layers

1. Prepare three 8-inch cake pans with parchment paper circles in the bottom and grease the sides. Preheat oven to 350°F (176°C).
2. Combine the flour, baking powder, baking soda and salt in a medium sized bowl and set aside.
3. Add the butter, oil, and sugar to a large mixer bowl and beat together until light in color and fluffy, about 1 1/2 to 2 minutes. Do not skimp on the creaming time.
4. Add the vanilla extract and sour cream and mix until well combined.
5. Add the eggs one at a time, mixing until mostly combined after each. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
6. Add half of the dry ingredients to the batter and mix until mostly combined.
7. Combine the lemon juice, lemon zest and buttermilk then slowly add the mixture to the batter and mix until well combined.
8. Add the remaining dry ingredients and mix until well combined and smooth. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated. Do not over mix the batter.
9. Toss the blueberries with 1/2 a tablespoon of flour and gently toss to combine, then add the blueberries to cake batter and fold to combine.
10. Divide the batter evenly between the cakes pans and bake for 25-30 minutes, or until a toothpick comes out with a just few crumbs.
11. Remove the cakes from the oven and allow to cool for about 2-3 minutes, then remove to cooling racks to cool completely.

For the frosting

1. Add the cream cheese and butter to a large mixer bowl and beat until well combined and smooth.
2. Add about half of the powdered sugar and mix until well combined and smooth.
3. Add the vanilla extract and mix until well combined.
4. Add the remaining powdered sugar and mix until well combined and smooth. Add more or less powdered sugar, as desired for consistency purposes.
5. To put the cake together, use a large serrated knife to remove the domes from the top of the cakes so that they’re flat, if needed.
6. Place the first cake on a serving plate or a cardboard cake round.
7. Spread about 1 cup of frosting evenly on top of the cake,
8. Add the second layer of cake and another cup of frosting.
9. Top the cake with the remaining layer and frost the outside of the cake. Refer to my tutorial for frosting a smooth cake, if needed. To make the line pattern in the side of the cake, run a 9 inch offset spatula around the outside of the cake will turning your turntable. Start with the line at the bottom and work your way to the top.
10. Pipe swirls of frosting on the top of the cake and decorate with lemon slices and blueberries, if desired.