Perfect Party Cake
Recipe From Tartelette
For the Cake:
2 1/4 cups cake flour (1 cup cake flour = 1 cup all purpose - 2 Tbs)
1 tablespoon baking powder
½ teaspoon salt
1 ¼ cups whole buttermilk
4 large egg whites
1 ½ cups sugar
2 teaspoons grated Meyer lemon zest
1 stick (8 tablespoons or 4 ounces) unsalted butter, at room temperature
½ teaspoon pure lemon extract

For the Buttercream:
1 cup sugar
4 large egg whites
3 sticks (12 ounces) unsalted butter, at room temperature
¼ cup fresh Meyer lemon juice

For Finishing:
1/2 cup seedless chocolate - raspberry preserves stirred vigorously or warmed gently until spreadable (for 2 cakes)
1/2 rhubarb preserves (for the other 2 cakes)
About 1 ½ cups white chocolate shavings
Macarons


Centre a rack in the oven and preheat the oven to 350 degrees F. Butter 4 4-inch round cake pans and line the bottom of each pan with a round of buttered parchment or wax paper. Put the pans on a baking sheet.
Sift together the flour, baking powder and salt.Whisk together the buttermilk and egg whites in a medium bowl.Put the sugar and lemon zest in a mixer bowl or another large bowl and rub them together with your fingers until the sugar is moist and fragrant. Add the butter and working with the paddle or whisk attachment, or with a hand mixer, beat at medium speed for a full 3 minutes, until the butter and sugar are very light.
Beat in the extract, then add one third of the flour mixture, still beating on medium speed. Beat in half of the buttermilk-egg mixture, then beat in half of the remaining dry ingredients until incorporated. Add the rest of the buttermilk and eggs beating until the batter is homogeneous, then add the last of the dry ingredients. Finally, give the batter a good 2- minute beating to ensure that it is thoroughly mixed and well aerated. Divide the batter between the four pans and smooth the tops with a rubber spatula.Bake for 30-35 minutes, or until the cakes are well risen and springy to the touch – a thin knife inserted into the centers should come out clean.
Transfer the cakes to cooling racks and cool for about 5 minutes, then run a knife around the sides of the cakes, unfold them and peel off the paper liners. Invert and cool to room temperature, right side up (the cooled cake layers can be wrapped airtight and stored at room temperature overnight or frozen for up to two months).

To Make the Buttercream:
Put the sugar and egg whites in a mixer bowl or another large heatproof bowl, fit the bowl over a plan of simmering water and whisk constantly, keeping the mixture over the heat, until it feels hot to the touch, about 3 minutes. The sugar should be dissolved, and the mixture will look like shiny marshmallow cream.
Remove the bowl from the heat. Working with the whisk attachment or with a hand mixer, beat the meringue on medium speed until it is cool, about 5 minutes. Switch to the paddle attachment if you have one, and add the butter a stick at a time, beating until smooth. Once all the butter is in, beat in the buttercream on medium-high speed until it is thick and very smooth, 6-10 minutes. During this time the buttercream may curdle or separate – just keep beating and it will come together again. On medium speed, gradually beat in the lemon juice, waiting until each addition is absorbed before adding more. You should have a shiny smooth, velvety, pristine white buttercream. Press a piece of plastic against the surface of the buttercream and set aside briefly.

To Assemble the Cakes: (directions for one, repeat for the other 3)
Using a sharp serrated knife and a gentle sawing motion, slice each layer horizontally in half. Put one layer cut side up on a cardboard cake round or a cake plate protected by strips of wax or parchment paper. Spread it with one third of the preserves. Cover the jam evenly with a layer of buttercream. Top with another layer, spread with preserves and buttercream and then do the same with a third layer. Place the last layer cut side down on top of the cake and use the remaining buttercream to frost the sides and top. Press the chocolate shavings into the frosting, patting it gently. Tint some remaining buttercream with your favorite colors and pipe large and small dots of different colors with plain decorating tips. You can also decorate with macarons (recipe here)

Serving:
The cake is ready to serve as soon as it is assembled, but it’s best to let it sit and set for a couple of hours in a cool room – not the refrigerator. Whether you wait or slice and enjoy it immediately, the cake should be served at room temperature; it loses all its subtlety when it’s cold. Depending on your audience you can serve the cake with just about anything from milk to sweet or bubbly wine.
Storing:
The cake is best the day it is made, but you can refrigerate it, well covered, for up to two days. Bring it to room temperature before serving. If you want to freeze the cake, slide it into the freezer to set, then wrap it really well – it will keep for up to 2 months in the freezer; defrost it, still wrapped overnight in the refrigerator.