For the Cake
- 2 3/ 4 cups cake flour
- 1 3/ 4 teaspoons baking powder
- 1 1/ 4 teaspoons baking soda
- 1 teaspoon kosher salt
- 2 teaspoons ground ginger
- 1 3/ 4 cups lightly packed dark brown sugar
- 1 3/ 4 cups whole buttermilk
- 3 large eggs
- 3/ 4 cup vegetable oil
- 2 teaspoons vanilla extract
For the Buttercream and Filling
- 2 cups unsalted butter, at room temperature
- 4 cups powdered sugar
- 1 tablespoon meringue powder, optional
- 1 small lemon, zested
- 2 teaspoons lemon extract
- 1 teaspoon vanilla extract
- 1/ 8 teaspoon kosher salt
- 2 tablespoons milk, or cream, if needed
- 10 ounces lemon curd
- 1 1/ 2 cups crushed or crumbled ginger cookies
To Make the Cake
Preheat the oven to 350ºF and spray three 8-inch cake pans with non-stick spray.
In a large bowl, sift together the flour, baking powder, baking soda, salt and ginger. In a separate bowl, whisk together the brown sugar, buttermilk, eggs, oil and vanilla. Add the wet ingredients to the dry, and whisk just until smooth and combined. Divide the batter evenly between the pans.
Bake cakes for about 28 minutes, until a cake tester in the center comes out clean. Set the pans on a wire rack, cover loosely with a clean kitchen towel, and cool completely.
To Make the Buttercream and Assemble
In the bowl of your stand mixer fitted with the whisk attachment, beat the butter for one minute. With the mixer on low, add the powdered sugar and meringue powder, mixing to combine. Add the lemon zest, lemon extract, vanilla and salt, then increase speed to medium and whip for about 5 minutes, scraping the bowl occasionally, until very light and fluffy, adding the milk if needed to slightly thin the buttercream.
Remove the cooled cakes from the pans and use a sharp knife to split each layer so that you have six thin layers. Handle the cake layers gently; when split, they can break apart very easily when you're picking them up. Use a large cake lifter, if needed, to move them from your counter onto the cake.
Place one cake layer, cut side up, on a cake board or cake pedestal. Spread thinly with 1/5 of the lemon curd and sprinkle with 1/5 of the crumbled cookies. Place the next cake layer on top, and repeat with the lemon curd and cookies until you've filled and stacked all the layers. The last cake should be placed on top with the cut side down. If you have any uneven areas around the sides, trim them with a sharp knife so that the cake is basically even and straight all the way around.
Frost the sides and top with a thin crumb coat of buttercream. Chill the cake for at least 30 minutes.
Fit a piping bag with Wilton tip 1M, and fill the bag with buttercream, then pipe the buttercream on in angled rows up the sides. Finish with a large spiraled rosette on top of the cake.