Preheat your oven to 350°F (175°C) and grease two 9-inch round cake pans. Line the bottoms with parchment paper.

In a medium-sized bowl, whisk together the flour, baking powder, baking soda, and salt until no lumps remain.

In a large mixing bowl, cream together the unsalted butter and sugar until light and fluffy using a hand mixer.

Add the eggs, lemon zest, lemon juice, and vanilla extract to the creamed mixture and beat until combined.

Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just combined.

Incorporate the buttermilk, stirring gently until the batter is smooth.

Divide the batter evenly between the prepared cake pans and bake for 25-30 minutes or until a toothpick inserted comes out clean.

Allow the cakes to cool in the pans for about 10 minutes before inverting them onto wire racks to cool completely.

While the cakes cool, whip the heavy whipping cream with powdered sugar and vanilla extract until stiff peaks form.

Once cooled, assemble by layering the cakes with Chantilly cream and optional lemon curd in between layers.

Refrigerate for at least 1 hour to set before slicing and serving.