Lemon Layer Cake with Vanilla Bean Frosting

Lemon Layer Cake with Vanilla Bean Frosting

Cake:
3 cups cake flour
1 tablespoon baking powder
1/2 teaspoon salt
16 tablespoons unsalted butter, at room temperature
Zest of 1/2 a lemon
2 cups sugar
5 large eggs, at room temperature
1 1/4 cups buttermilk, at room temperature
1 tablespoon lemon extract
1 teaspoon vanilla

Filling:
4 ounces mascarpone or cream cheese, cold
2 1/2 tablespoons butter, at room temperature
1 1/4 cups powdered sugar, sifted
2 teaspoons lemon extract
Zest of 1/2 a lemon
1 cup heavy cream

Frosting:
1 1/2 cups plus 2 tablespoons unsalted butter, at room temperature
3 cups powdered sugar
Pinch of salt
1 vanilla bean, split lengthwise
1 teaspoon vanilla
2 tablespoons heavy cream

Candied lemon slices:
1-2 lemons
1 cup sugar
1 cup water

Cake:
To make the cake, preheat the oven to 350 degrees.  Butter and flour the edges of three 8 inch round cake pans and shake out excess.  Set aside.  Line the bottoms of the pans with parchment paper.

In a medium mixing bowl, combine the cake flour, baking powder and slat.  Whisk together and set aside.  Add the butter to the bowl of an electric mixer fitted with the paddle attachment.  Add the lemon zest to the bowl of the mixer with the butter.  Beat on medium-high speed for 3 minutes, until light and creamy in color.  Scrape down the sides of the bowl and beat for 1 more minute.
Add the sugar to the butter mixture, 1/4 cup at a time, beating 1 minute after each addition.  Mix in the eggs, one at a time until incorporated.  scrape down the sides of the bowl after each addition.  Combine the buttermilk and the lemon and vanilla extract in a liquid measuring cup.  With the mixer on low speed, add the dry ingredients alternately with the wet ingredients, beginning and ending with the dry ingredients and mixing just until incorporated.  Scrape down the sides of the bowl and mix for 15 seconds longer.

Divide the batter between the prepared baking pans.  Bake until golden and a toothpick inserted in the center comes out clean, about 20-22 minutes, rotating the pans halfway through baking.  Let cool in the pans about 10 minutes, then invert onto a wire rack and let cool completely.

Filling:
Combine the mascarpone and butter in the bowl of an electric mixer.  Beat on medium-high speed until smooth and well combined.  Mix in the powdered sugar and beat on low speed until incorporated.  Blend in the lemon extract and lemon zest.  Increase the speed to medium-high and beat until light and fluffy, about 2 minutes.  Transfer the mixture to a medium bowl and set aside.  Wipe out the mixer bowl and fit with the whisk attachment.  Add the heavy cream to the bowl and whip on high speed until stiff peaks form, being careful not to overbeat.  Mix about a third of the whipped cream into the lemon-mascarpone mixture to lighten.  Gently fold in the remaining whipped cream until no steaks remain and the mixture is evenly blended.

Frosting:
Add the butter to the bowl of an electric mixer fitted with the whisk attachment.  Whip on medium-high speed until smooth, about 1 minute.  Add the powdered sugar to the bowl and mix on medium-low speed just until incorporated.  Scrape the seeds from the vanilla bean pod into the bowl and add in the salt.  Continue to beat on medium-high speed until smooth, about 1-2 minutes.  Mix in the vanilla extract and heavy cream on low speed just until incorporated.  Increase the mixer speed and whip on high speed until light and fluffy, scraping down the bowl as needed, about 4 minutes.

Candied lemon slices:
wash and dry the lemons thoroughly.  Use a sharp serrated knife to make very thin slices of lemon.  Poke out any seeds in the slices with a toothpick.  Combine the sugar and water in a medium saucepan over medium-high heat.  Heat the mixture until the sugar dissolves.  Add the lemon slices to the mixture so that they are in a single layer, reduce the heat to medium-low and let simmer for about 20 minutes, turning the slices at least once so both sides are candied.  Remove from the heat.  Store in a container with the syrup until ready to use.

Assemble:  Place one of the layers on a serving platter.  Top with half of the lemon-masarpone mixture and smooth in an even layer.  Place a second cake layer on top of the filling and to with the remaining filling.  Place the final cake layer on top.  Frost the top and sides of the assembled cake with the vanilla frosting.  Garnish with the candied lemon slices.