Lemon Poppy Seed Cake 

1. Preheat the oven to 325F(165C). Grease and line an 8×8 inch square baking pan with parchment paper.
2. In a medium mixing bowl, add and whisk to combine the flour, baking powder and salt.
3. In the bowl of a stand mixer or a large mixing bowl, add the sugar and lemon zest. Use a fork or fingertips to incorporate lemon zest into sugar until sugar becomes fragrant with the aroma of lemons.
4. Fit stand mixer with paddle attachment or use a hand-held electric mixer to cream the butter, oil and lemon sugar together at medium high speed until mixture appears thick and fluffy in appearance, about 2-3 minutes.
5. Mix in the vanilla extract into the creamed butter mixture.
6. Beat the eggs into the wet mixture one at a time. The initial egg should be completely mixed into the batter before mixing in the next egg.
7. Reduce mixer speed to low. In an alternating fashion, starting and ending with the dry ingredients, mix half of the dry ingredient mixture into the wet batter, followed by the buttermilk and lemon juice, and ending with the remaining dry ingredient mixture.
8. Next, mix in the poppy seeds into the cake batter.
9. Stop the mixer and use a spatula to scrape the sides and base of the mixing bowl.
10. Resume mixing the cake batter at medium speed for an additional 30-60 seconds to help ensure an evenly smooth batter.
11. Transfer cake batter into prepared baking pan and bake for 30-35 minutes, rotating the pan halfway through bake time. Cake is ready once a toothpick inserted into the center of the cake comes out clean.
12. Allow the cake to cool in the baking pan for 5-10 minutes before transferring to a cooling rack to cool completely to room temperature. 

Blueberry Buttercream

1. Grind the freeze dried blueberries into a powder in a coffee grinder or small food processor. You should end up with about 1 1/2 tablespoons of powdered freeze-dried blueberries.
2. In a stand mixer fitted with paddle attachment or in a large mixing bowl with a hand-held electric mixer, cream the butter and salt (optional) at medium high speed until it is smooth and fluffy in appearance, about 2-3 minutes.
3. Reduce the mixer speed to low and mix in the confectioners’ sugar and powdered freeze-dried blueberries into creamed butter. Gradually increase the mixer speed back to medium.
4. Once all the sugar and powdered blueberries have been incorporated into the butter, mix in 1 tablespoon of the heavy whipping cream and vanilla extract (optional) into buttercream.
5. If buttercream appears too thick, mix in additional cream 1/2 tablespoon at a time until the desired consistency (thick but spreadable) is reached.
6. If buttercream appears to be too soft, mix in additional confectioners’ sugar 1/4 cup at a time until a thick but spreadable consistency is reached.
7. Increase mixer speed to medium high and mix blueberry buttercream for an additional 30-60 seconds. The resulting buttercream should be smooth and fluffy in appearance.

Assembly

1. Spread a thin layer of the buttercream over the cooled cake.
2. Transfer the remaining buttercream into a large pastry bag fitted with a 6B French or desired pastry tip.
3. Pipe buttercream in a braid pattern over the entire surface of the cake. This is the buttercream braid tutorial I used.
4. Alternatively, buttercream may be evenly spread over the surface of the cooled cake for a more rustic cake design.