Preheat your oven to 350°F (175°C). Grease and flour two 8-inch round cake pans, and line the bottoms with parchment paper for easier release.

In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.

In a large mixing bowl, combine the sugar, oil, eggs, lemon zest, lemon juice, and vanilla extract. Beat until the mixture is light and creamy.

Add the dry ingredients to the wet mixture in three parts, alternating with the buttermilk. Start and end with the flour mixture, mixing just until combined. Be careful not to overmix, as this can lead to a dense cake.

In a small bowl, toss the blueberries with 1 tablespoon of flour (this helps prevent them from sinking to the bottom). Gently fold the berries into the batter with a spatula.

Divide the batter evenly between the two prepared pans. Smooth the tops and bake for 28–32 minutes, or until a toothpick inserted into the center comes out clean. Allow the cakes to cool in the pans for 10 minutes before turning them out onto a wire rack to cool completely.

In a chilled mixing bowl, beat the heavy cream until soft peaks form. Add the powdered sugar, lemon juice, and zest, and continue whipping until stiff peaks form. Be careful not to overwhip—it should be fluffy and spreadable.

Once the cakes are fully cooled, place one layer on your serving plate. Spread a generous layer of the whipped lemon frosting over the top, then add the second cake layer. Frost the top and sides with the remaining frosting. Garnish with extra blueberries or lemon zest if desired.