• Preheat the oven to 350°F/180°C and grease two 9-inch cake pans.
• In a medium-sized bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
• Using a mixer fitted with the whisk attachment, beat together the eggs and sugar on high speed until pale and fluffy, about 5 minutes.
• With the mixer running on low, slowly add the oil. Then continue with the melted butter, buttermilk, lemon juice, zest, and vanilla. Mix until combined.
• Gradually add the flour mixture and mix until just combined, taking care not to overmix.
• Divide the batter evenly between the two prepared pans.
• Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean or with a few crumbs. Allow to cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.

For the Lemon Curd Filling:

• In a medium saucepan, melt the butter over medium heat with the sugar and salt. Stir until the butter is melted and the sugar is incorporated.
• In a separate bowl, whisk together the lemon zest, eggs, egg yolk, lemon juice, and cornstarch.
• Slowly pour a small amount of the hot butter mixture into the egg mixture, whisking constantly to temper the eggs.
• Pour the tempered egg mixture back into the saucepan and whisk continuously over medium heat until thickened and just starting to bubble, about 8 minutes.
• Strain the curd through a sieve into a clean bowl to remove any lumps or zest. Cover with plastic wrap, placing the wrap directly on the surface to prevent a skin from forming. Allow to cool to room temperature, then refrigerate until fully chilled.

For the Cream Cheese Frosting:

• In a large mixing bowl, beat the softened cream cheese and butter together using an electric mixer on medium speed until they are smooth and creamy. Scrape down the sides of the bowl as needed to ensure even mixing.
• Add the powdered sugar, one cup at a time, to the cream cheese and butter mixture. Continue to beat on low speed after each addition until the sugar is fully incorporated. Scrape down the sides of the bowl occasionally.
• Add the vanilla extract and a pinch of salt to the frosting mixture. Beat again on medium speed until everything is well combined and the frosting has a smooth consistency. At this point, taste the frosting and adjust the sweetness or flavor if necessary.
• If the frosting seems too thick for your liking or if you prefer a softer consistency, you can add a few tablespoons of milk or heavy cream. Start with one tablespoon at a time, and mix well until you achieve the desired consistency.

Assembling the Cake:

• Place one of the cake layers on a cake stand or serving plate. Pipe the cream cheese frosting around the edge of bottom layer. Then fill the center of the piped frosting with the lemon curd. Carefully place the second cake layer on top.
• Apply a thin layer of frosting on the top and around the sides of the cake. This thin layer is what creates the semi-naked look, allowing some of the cake to show through. If you want a more defined semi-naked look, use the offset spatula to gently scrape off some of the frosting around the sides of the cake until you achieve the desired effect.
• You can now decorate the top of the cake as desired with fresh berries, edible flowers, or any other decorations of your choice.
• Once the cake is decorated, refrigerate it for at least 30 minutes to set the frosting before serving.