Triple Lemon Cake

This is the cake my blog is named for and this is the cake Jake and Alice chose as their wedding cake--it is a wonderful and beautiful cake!
For the cake:
9-1/4 oz. (2-1/3 cups) cake flour; more for the pans
2-3/4 tsp. baking powder
1/4 tsp. table salt
1-3/4 cups granulated sugar
2 Tbs. lightly packed finely grated lemon zest
6 oz. (3/4 cup) unsalted butter, completely softened at room temperature; more for the pans
1 cup whole milk, at room temperature
 5 large egg whites, at room temperature
1/4 tsp. cream of tartar

 For the filling: 1 recipe Lemon Curd, chilled

 For the frosting:
8 oz. (1 cup) unsalted butter, completely softened at room temperature
2 Tbs. lightly packed finely grated lemon zest
3-1/2 cups sifted confectioners’ sugar 3 Tbs. fresh lemon juice


 -------------------------------------------------------------------------------- Make the cake: Position a rack in the middle of the oven; heat the oven to 350°F. Generously butter and flour two 8 x 2-inch round cake pans. Sift the cake flour, baking powder, and salt together into a medium bowl. Pulse 1/4 cup of the sugar with the zest in a food processor until well combined. In a large bowl, beat the butter and lemon sugar with an electric mixer on medium speed until light and fluffy (about 1-1/2 minutes). Add the remaining 1-1/2 cups sugar and beat until smooth (about 1-1/2 minutes). Beat in a quarter of the milk just until blended. On low speed, add the flour mixture alternately with the milk in three batches, scraping the bowl with a rubber spatula; beat just until blended. In another large bowl, beat the egg whites with an electric mixer (with clean beaters or the whip attachment) on medium speed just until foamy. Add the cream of tartar, increase the speed to medium high, and beat just until the whites form stiff peaks when the beaters are lifted. Add a quarter of the whites to the batter and gently fold them in with a whisk or a rubber spatula; continue to gently fold in the whites, a quarter at a time, being careful not to deflate the mixture. Divide the batter evenly between the prepared pans. Smooth the tops with the spatula. Bake until a pick inserted in the centers comes out clean, 35 to 40 minutes. Let cool in the pans on a rack for 10 minutes. Run a table knife around the inside of the pans and carefully invert each cake out onto the rack. Flip them right side up and let cool completely. With the palm of one hand pressed on top of a cake layer, cut each in half horizontally, using a long serrated knife. Put one of the four cake layers on a serving plate, cut side up. With an offset spatula or a table knife, spread a generous 1/3 cup chilled lemon curd on top of the cake layer. Lay another cake layer on top, spread it with another generous 1/3 cup lemon curd, and repeat with the third cake layer, using the last 1/3 cup lemon curd. Top with the fourth cake layer. Make the frosting: In a medium bowl, beat the butter and lemon zest with an electric mixer on medium speed until light and fluffy. Add the confectioners’ sugar in batches and beat until light and fluffy. Add the lemon juice and beat for 1 minute. (You can make the frosting a couple of hours ahead and keep it, covered, at cool room temperature.) Frost the cake: Up to a few hours before serving, spread a thin layer of frosting on the cake, filling in any gaps as you go. Chill until the frosting firms a bit, about 1/2 hour. (This "crumb coat" will keep crumbs from catching on your spatula and marring the finished cake.) Spread the remaining frosting decoratively over the top and sides of the cake. Scatter with bits of lemon zest and dragees, or garnish as you like.