Preheat the oven to 350°F/177°C and prepare three 6-inch or two 8-inch cake pans by spraying the sides with baking spray and fitting a parchment paper circle to the bottom of each pan.

In a medium bowl, add the flour, baking powder, baking soda and salt. Whisk together and set aside.

In the bowl of a stand mixer fitted with the paddle attachment, beat the butter at high speed until creamy, about 2 minutes. Add the sugar and cream it together with the butter at medium-high speed until light and fluffy, about 2 minutes, scraping the bowl and paddle at the halfway point.

Turn the mixer to low and add the egg whites one at a time, mixing until they are just combined and scraping down the bowl and paddle as needed. Add the vegetable oil and vanilla, increase the mixer speed to high and beat for 1 minute.

Turn the mixer off and add the flour mixture all at once. Mix the ingredients on low speed until just combined, then slowly pour in the buttermilk. Continue mixing at low speed for about 30 seconds, until the batter is uniform and combined. The batter will be slightly thin.

Divide the batter evenly between the prepared cake pans and bake for 28 to 32 minutes. They’re done when they spring back to the touch and a toothpick inserted into the centers comes out clean or with just a few moist crumbs on it.

Let the cakes cool in their pans for 5 minutes, then remove them from the pans and allow them to cool completely on a wire rack.

Prepare the double-boiler: Fill a saucepan with a few inches of water and set over medium heat. Make sure that the mixing bowl you’ll be using for the next step fits on top of it without the bottom of the bowl touching the water, then remove the mixing bowl and bring the water in the saucepan to a simmer.

Separate the eggs: it’s really important not to get even a drop of egg yolk in your egg whites, so I recommend separating one egg white at a time into a small bowl, then adding each egg white into your heat proof mixing bowl (glass or metal).

Add the sugar into your egg whites and whisk together to combine, then set the bowl over the saucepan of simmering water. Whisk constantly until the mixture has thinned out and the sugar is fully dissolved, 4-5 minutes.

While the mixture is still warm, transfer it to the bowl of your stand mixer fitted with the whisk attachment. Turn the mixer to medium-high speed and beat until stiff peaks form, 10-15 minutes.

Once the meringue has cooled, switch the stand mixer to the paddle attachment. Turn the mixer to medium-high and add the butter 1 Tablespoon at a time. After all the butter has been added, turn the mixer down to medium speed and beat in the vanilla and salt, about 30 seconds.

Once the white cake layers are completely cooled, level them to your desired height. Add a swipe of Swiss meringue buttercream onto a cardboard cake circle and place the first cake layer on top. Fill and stack the cake with Swiss meringue buttercream, then crumb coat the cake.

Refrigerate the cake for 15-20 minutes to let the crumb coat firm up before frosting the cake with the rest of the Swiss meringue buttercream.

To create the design pictured, use a small spatula to create a rustic textured finish on the sides of the cake and keep the top edge raw. Garnish with a crescent formation of fresh berries.