Heat your oven to 350°F. While it preheats, grease three 6-inch round cake pans with butter or cooking spray, then dust the bottoms and sides with flour, tapping out any excess. Line the bottom of each pan with parchment paper for easy removal later. This prep work ensures your cakes will release cleanly and bake evenly.

In a medium bowl, whisk together the flour, baking powder, and sea salt—set aside. In a separate large bowl, beat the room-temperature butter on medium speed until it's smooth and pale, about 1-2 minutes. This creaming process incorporates air into the butter, which helps the cake rise. Add the sugar and continue beating for 2-3 minutes until the mixture is light and fluffy, scraping down the bowl as needed.

Add the room-temperature eggs to the butter-sugar mixture one at a time, beating well after each addition—this ensures they're fully incorporated. Pour in the vanilla extract and mix until combined. Now add the dry ingredient mixture from Step 2 and the buttermilk in alternating additions, starting and ending with the dry mixture (dry, wet, dry, wet, dry). Scrape down the bowl between additions to ensure even mixing. I find that starting and ending with flour prevents the batter from becoming too wet or breaking—this technique ensures a tender, moist crumb.

Divide the batter evenly among the prepared pans from Step 1—about 1.5 cups per pan. Smooth the tops with a spatula. Bake in your preheated 350°F oven for 30-35 minutes, until a toothpick inserted in the center comes out clean or with just a few moist crumbs. The cakes should be golden brown on top. Allow them to cool in the pans for 10 minutes, then turn them out onto a wire cooling rack to cool completely.

While the cakes are baking, combine the 2 cups of blueberries, water, 1/2 cup sugar, lemon juice, and cinnamon in a saucepan over medium-high heat. Bring to a boil and cook for 2 minutes, stirring occasionally. The berries will begin to break down and release their juices. Whisk the cornstarch slurry (cornstarch mixed with water) to recombine it, then stir it into the boiling berries. Continue cooking for 30-60 seconds, stirring constantly, until the mixture thickens and turns glossy. Remove from heat and let cool to room temperature—the compote will thicken further as it cools. I like to make the compote while the cakes bake so everything is ready at the same time.

Pour the heavy whipping cream into a chilled bowl (chilling prevents the cream from breaking) and whip on medium-high speed until it begins to thicken. Add the powdered sugar and continue whipping until stiff peaks form—this takes about 2-3 minutes total. Be careful not to overbeat, or you'll end up with butter. Use the whipped cream immediately or refrigerate until assembly.

Place one cooled shortcake layer on a serving plate. Top with a layer of whipped cream from Step 6, then spoon some of the cooled blueberry compote from Step 5 over the cream. Add the second cake layer, repeating the cream and compote layers. Top with the final cake layer and finish with a dollop of whipped cream and a handful of fresh blueberries. Serve immediately while the cake is still moist and the flavors are fresh. For the most elegant presentation, I like to gently press a few fresh berries into the top layer of cream so they're visible.