Preheat oven to 350° F. Grease two 8 inch (or 9) round cake pans. Dust pans with flour and tap out excess any excess.

Make glaze by combining the sugar, lemon juice and elder flower liquor. Set aside.

In a stand mixing bowl with a paddle attachment combine the butter and 1 ½ cups sugar. Turn on a low speed and let run. Add lemon zest.

In a measuring cup combine milk and lemon juice. It will curdle. Set aside.

To butter and sugar mixture add: olive oil, vanilla if you so choose, rosemary (unless you already added it to the buttermilk) and egg yolks. Beat for a couple of minutes.

In another mixing bowl on your stand mixer fitted with whisk attachment, beat egg whites at medium speed until foamy. With machine running, stream in the remaining ¼ cup sugar. Beat at high speed just until stiff peaks form. Set aside.

Add baking soda, baking powder, and salt to the butter mixture and mix briefly. Add the cornstarch and half the flour to the butter mixture.

Add in the homemade buttermilk (milk and lemon juice).

Add the rest of the flour and beat until just incorporated.

Scrape down the bowl and ensure it’s incorporated with as little mixing as possible.

Using rubber spatula, gently fold in the egg white mixture until just incorporated. Be gentle! The air staying in the batter is the whole point.

Divide batter evenly between your prepared cake pans.

Place pans on a cookie sheet pan and bake on the center rack in the oven at 350° F for 20-25 minutes. Unless you’re absolutely certain your over is very even, rotate pans halfway through. The cake will begin pulling away from the edge of the pan. You can use a toothpick to ensure the batter isn’t still wet in the center.

Cool cakes in pans for 5-10 minutes.

Using a skewer poke holes all over the whole surface of both cakes.

Pour glaze ½ of the glaze evenly over the surface of each of the two cakes. Allow to cool completely (about 1 more hour) before frosting.

Frosting: Combine all ingredients in the bowl of a stand mixer fitted with a paddle attachment. Mix on medium speed until combined and creamy. Scrape down the bowl as needed.

Place one cake on a platter. Top with about ⅓ of the frosting. Spread evenly. Place second cake on top. Frost the cake. Garnish with rosemary and lemon slices.