Perfect Party Cake - Daring Bakers Challenge #2 Completed

I was supposed to post this Daring Baker challenge on March 30, but was out of town, so better late than never!
I made this cake for Easter. It was yummy - I skipped the buttercream frosting, because I like it a little lighter - so I made frosting with cool whip, crushed pineapple and coconut cream pudding mix.

Perfect Party Cake
adapted from Dorie Greenspan's Baking: From My Home to Yours
makes 12 to 14 servings
Cake
9 oz cake flour
1 tablespoon baking powder
1/2 teaspoon salt
10 3/4 fl. oz. buttermilk
4 large egg whites
10 1/2 oz sugar
2 teaspoons grated lemon zest
4 oz unsalted butter, room temperature
1/2 teaspoon lemon extract
Buttercream
7 oz sugar
4 large egg whites
12 oz unsalted butter, room temperature, cut into 1-in pieces
2 1/4 fl. oz. fresh lemon juice
1 teaspoon vanilla extract
For finishing
2/3 cup seedless raspberry preserves
1 1/2 cups sweetened shredded coconut
Preheat the oven to 350 degrees F. Spray or butter two 9" x 2" round cake pans. Line the bottom of each cake pan with a buttered parchment circle.
For the cake: Sift together the cake flour, baking powder, and salt.
Whisk the buttermilk and egg whites together in a separate bowl.
Combine the sugar and lemon zest in a stand mixer bowl and rub together with your fingers until the sugar is moist and smells like the lemon.
Add the butter to the mixer bowl and beat together with the sugar for 3 minutes on medium speed until the mixture is fluffy and light.
Add in the vanilla extract.
Add in the flour and buttermilk mixtures in alternating additions, starting and ending with the flour mixtures. Be sure each addition is fully incorporated before adding the next.
When everything is added beat the batter for an additional 2 minutes.
Divide the batter between the two pans and bake for 30 minutes in the oven or until the tops are set and springy, and a cake tester inserted into the centers come out clean.
Transfer the pans to wire racks and let cool for a few minutes, then flip and unmold the cakes (run a knife around the sides of the cakes if necessary). Peel the parchment off and flip the cakes back over right side up on the wire racks to finish cooling.
The fully cooled cake layers can be wrapped in plastic and kept overnight or frozen for up to 2 months.
For the buttercream: Combine the sugar and egg whites in a medium heatproof bowl and place over a pan of simmering water.
Whisk the sugar mixture constantly over heat until the sugar is dissolved and the mixture looks smooth and shiny, about 3 minutes.
Remove mixture from heat and pour into a stand mixer bowl. Whisk on medium speed for about 5 minutes until the mixture has cooled.
Switch to the paddle attachment and with the speed on low, add the butter a few pieces at a time, beating until smooth.
When all the butter has been added, beat the buttercream on medium-high speed for about 6-10 minutes until it is very thick and smooth.
Add in the lemon juice and beat until combined. Add in the vanilla.
The buttercream is ready to be used. Place a piece of plastic wrap against the surface until you are ready to use it to prevent it from drying out.
To assemble the cake: Using a sharp serrated knife, slice each cake layer horizontally in half - Stir the raspberry preserves until it is loose and spreadable.
Place a layer on a cardboard cake round, cut side up. Spread about a third of the raspberry preserves on the cake layer.
Spread a layer of buttercream on top of the preserves. Top with a second cake layer. I found that if you have problems with this, you can spread the buttercream on a second cake layer and flip it over onto the preserve-covered layer - but you have to be very careful doing this or you'll break your cake layer!
Spread preserves and buttercream on the second cake layer as you did with the first. Top with a third cake layer.
Spread preserves and buttercream on the third cake layer as you did with the second. Top with the last cake layer, cut side down.
Use the rest of the buttercream to frost the sides and top of the cake.
Press the coconut over the sides and top of the cake.
The cake is best served a couple of hours after it is assembled to let the flavors develop. You can refrigerate it for up to 2 days, but be sure it is well covered or the cake will dry out. You should also let the cake come to room temperature before you serve it as it does not taste as good cold.