Cake

1. Preheat the oven to 350F/180C and heavily grease two 8-inch cake pans or two 9-inch cake pans, and set them aside. Your oven must be properly preheated for your cake to bake properly.
2. In a bowl of an electric stand mixer fitted with a paddle attachment or a large bowl with an electric handheld mixer combine the cake flour, baking powder, baking soda, salt, lemon zest, and granulated sugar. Once fully combined for 30-60 seconds add the softened butter in chunks and mix until incorporated and the mixture becomes like wet sand.
3. In a bowl combine the buttermilk, sour cream, oil, lemon juice, and lemon emulsion then add to dry ingredients and mix for 60 seconds, you want to really incorporate everything to make sure the batter builds structure. Add in the eggs and mix for an additional 45-60 seconds, there should be no trace of egg left. Use a rubber spatula to scrape the bottom of the bowl to make sure everything is evenly combined. In a small bowl combine the blueberries and flour. Gently mix in 3/4 of the berries into the cake batter. Pour cake batter into prepared pans and top with remaining blueberries scattered on top, gently press into cake batter ever so slightly. 
4. Quickly and gently place the pans in the oven and do not open the oven door until at least the 25-minute mark, if you have an oven light use it! Do this very quickly and don't close the door too abruptly. Your cakes should be done baking in the 33-38 minutes mark for 8-inch cakes. If you press a toothpick into the center it should come out with no wet batter, or you can gently press the top center of the cake and it should bounce bake immediately, the sides of the cake will be coming away from the edges of the pan. Set on a wire rack to cool for 30 minutes before inverting onto the wire rack to cool completely before decorating.

Frosting

1. In the bowl of an electric mixer with a whisk attachment whisk the cream cheese, lemon emulsion, and powdered sugar for 2 minutes. Make sure to scrape down the bowl once or twice to ensure everything is evenly incorporated.
2. While the mixer is still on medium-high speed very slowly pour/stream in the heavy cream. Whip for another couple of minutes after the cream has been added until you get a thick whipped cream texture do not over-mix. You want stiff peaks though so let it get nice and fluffy. The texture should be like a thick whipped cream not like buttercream frosting.
3. Using a serrated knife saw off the dome of the cake to create a flatter, even surface. Then slice the cake in half. Place the bottom layer on the serving plate and place two large ice cream scoops of frosting on the cake then use a small angled spatula to spread an even layer of frosting onto the first cake layer then top with the second cake layer upside down to create a flatter top surface. Make sure to get down and look at the cake at eye level to see if it is level or not, and adjust as necessary. Repeat with the second layer of cake by slicing it in half and frosting it. Add a thin layer of frosting around the whole cake to create a crumb coat, then place the cake in the fridge for 30 minutes or freezer for 10 minutes to set it. Frost with remaining frosting and add blueberries to the cake and lemon zest. Since this is a soft frosting I like to set the cake in the freeze or fridge for 15 minutes to set up. 
4. Store the cake in an air-tight container in the refrigerator for up to 5 days, although best tasting the first two days. For best results, let the cake come to room temperature for 10-15 minutes before enjoying a slice.