Vanilla Lemon Layer Cake

A light vanilla and lemon scented layer cake filled with lemon curd and iced with vanilla italian meringue buttercream.
Ingredients
FOR THE CAKE:
3 cups cake flour (325 grams)
2 cups sugar (400 grams)
4 ½ teaspoons baking powder (12 grams)
½ teaspoon salt (2 grams)
One vanilla bean
1 cup + 2 tablespoons unsalted butter , at room temperature (254 grams)
1 ⅓ cup whole milk (11 fl oz)
5 large egg whites
1 tablespoon vanilla extract
FOR THE LEMON CURD:
1 cup unsalted butter , cut into cubes (113 grams)
1 cup granulated sugar (230 grams)
1 cup freshly squeezed lemon juice (8 fl oz, about 3-4 lemons)
Zest of 3 lemons
10 large egg yolks
FOR THE ITALIAN MERINGUE BUTTERCREAM:
1 cup granulated sugar (230 grams)
¼ cup water (2 fl oz)
4 large egg whites
2 cups unsalted butter , at room temperature (1 pound, 452 grams)
1 tablespoon vanilla extract
Instructions
TO MAKE THE CAKE:
Preheat oven to 350°F. Butter and flour three 8-inch cake pans and line with parchment paper.
In the bowl of a stand mixer fitted with a fitted attachment combine the cake flour, sugar, baking powder, and salt. Mix for 30 seconds. Use a paring knife to cut the vanilla bean in half and scrape the seeds from the pod. Add the vanilla seeds, butter, and 1 cup of the milk to the dry ingredients. Mix on low speed for 1 minute until combined, then increase the speed to high and beat until light and fluffy, about 3-4 minutes, scraping the bowl down as needed.
In a small bowl, combine the remaining ⅓ cup milk, egg whites and vanilla extract. Add to the mixture in the stand mixer in 3 additions, mixing after each addition until smooth.
Divide the batter between the 3 prepared pans and bake until lightly golden and a toothpick inserted into the center comes out clean, about 30 minutes. Let sit in the pan 10 minutes, then turn out onto a wire rack to cool completely.
Can be baked in advance. Store tightly wrapped in plastic wrap in the fridge for up to 5 days, or in the freezer (double wrapped) for a few months.
Place one cake layer on a cake stand or display plate. Fill a pastry bag with a small round tip with 1 cup of the buttercream. Pipe a wall of icing around the edge of the cake layer. Spoon approximately 1 cup of the lemon curd into the center and spread evenly. Repeat with the next cake layer. Place the third cake layer on top and ice the entire cake with the remaining buttercream.
Store the cake in the fridge for up to 4 days. Let come to room temperature before serving for best results.
TO MAKE THE LEMON CURD:
In a large saucepan combine ½ cup of the butter butter, ½ cup of the sugar, lemon zest, and lemon juice and bring to a boil, stirring occasionally to dissolve the sugar.
In another bowl, whisk together the egg yolks and the remaining ½ cup sugar. Slowly add the heated lemon juice mixture into the egg yolk mixture, whisking continuously. When fully combined, return the mixture to the saucepan and continue to cook until thickened, about 4-5 minutes. Whisk in the remaining ½ cup butter until melted and smooth.
Remove from heat and strain through a fine mesh strainer into a shallow dish. Place plastic wrap directly on top of the curd to prevent a skin from forming and chill in the fridge for at least 30 minutes.
Can be made in advance. Store in the fridge for up to one week.
TO MAKE THE ITALIAN MERINGUE BUTTERCREAM:
Combine the water and sugar in a saucepan over medium heat. Bring the mixture to a boil, stirring occasionally. Once it boils, stop stirring and insert a candy thermometer.
Meanwhile, whip the egg whites in the bowl of a stand mixture to soft peaks. When the sugar is at 238 degrees, add it to the egg whites in a slow steady stream with the mixer on medium speed.
Increase the speed to high and beat until cooled to room temperature.
Add the butter a few tablespoons at a time, while continuing to mix on medium high speed. Add the vanilla. Increase the speed to high and beat until smooth.