First, the oven should be preheated to 350°F (175°C). Next, three 8-inch round cake pans need to be greased with butter or cooking spray. Then, the bottoms should be lined with parchment paper circles. Finally, the parchment paper should be greased as well to ensure easy release.

To begin, the flour, baking powder, baking soda, and salt should be whisked together in a medium bowl. These dry ingredients should then be set aside while the wet ingredients are prepared.

In a large mixing bowl, the softened butter and granulated sugar should be beaten together using an electric mixer. This mixture should be beaten on medium-high speed for approximately 3-4 minutes until it becomes light and fluffy. The mixture will appear pale yellow and have increased in volume.

Once the butter and sugar are properly creamed, the eggs should be added one at a time. Each egg should be fully incorporated before the next one is added. Following this, the vanilla extract, lemon extract, and lemon zest should be mixed in until well combined.

In a separate small bowl, the buttermilk, sour cream, and lemon juice should be whisked together. This creates a tangy liquid mixture that will keep the cake incredibly moist.

The dry ingredients should be added to the butter mixture in three additions, alternating with the buttermilk mixture. The process should begin and end with the dry ingredients. Between each addition, the batter should be mixed on low speed just until combined. Overmixing must be avoided to ensure a tender crumb.

Meanwhile, the fresh blueberries should be placed in a small bowl and tossed with 2 tablespoons of flour. This coating helps prevent the berries from sinking during baking. These flour-coated blueberries should then be gently folded into the batter using a rubber spatula.

The batter should be divided evenly among the three prepared cake pans. Each pan should be filled approximately two-thirds full. The surface of the batter should be smoothed with an offset spatula.

The pans should be placed in the preheated oven and baked for 28-32 minutes. The cakes are done when a toothpick inserted into the center comes out clean or with just a few moist crumbs. Additionally, the tops should spring back lightly when touched.

Once baked, the cakes should be allowed to cool in their pans for 10 minutes. After this initial cooling period, they should be carefully inverted onto wire racks. The parchment paper should be removed, and the cakes should be allowed to cool completely before frosting.

In a large bowl, the softened butter and cream cheese should be beaten together using an electric mixer. This should be done on medium-high speed for approximately 2-3 minutes until the mixture becomes smooth and creamy. No lumps should remain.

Next, the powdered sugar should be added gradually, one cup at a time. The mixer should be run on low speed initially to prevent a powdered sugar cloud. Once all the sugar has been incorporated, the mixer speed should be increased to medium-high.

The lemon juice, lemon zest, vanilla extract, and salt should then be added. The frosting should be beaten for an additional 2 minutes until it becomes light and fluffy. If the frosting seems too soft, it can be chilled in the refrigerator for 15-20 minutes.

Once the cake layers have cooled completely, any domed tops should be carefully leveled using a serrated knife. This creates flat, even layers that stack beautifully.

The first cake layer should be placed on a cake stand or serving plate. Approximately ¾ cup of frosting should be spread evenly over the top. The second layer should be positioned on top, and another ¾ cup of frosting should be applied. Finally, the third layer should be added.

A thin crumb coat should be applied to the entire cake first. This involves spreading a very thin layer of frosting over the top and sides to seal in any crumbs. The cake should then be refrigerated for 20-30 minutes to allow this layer to set.

After the crumb coat has firmed up, the remaining frosting should be applied generously to the top and sides of the cake. An offset spatula can be used to create smooth sides and a decorative swirl pattern on top.

Fresh blueberries, lemon slices, and edible flowers can be arranged on top of the cake for a beautiful presentation. The finished cake should be refrigerated until ready to serve, but it should be brought to room temperature 30 minutes before serving for the best flavor and texture.