Go Back

Lemon Bar Cake

Print Recipe
The classic Lemon Bar dessert turned into a beautiful cake! Shortbread crust baked right into every cake layer, zesty lemon curd made from scratch (it's super easy and you'll want to spread it on everything in sight!), my classic lemon cake (cannot be beat!), and lemon buttercream. Every bite was heavenly, and we seriously could not get enough of this cake.
Course Dessert
Servings 12 servings
Author Mandy Merriman

Equipment

  • three 6" cake pans, two 8" cake pans, 24 cupcakes
  • kitchen aid mixer
  • food processor
  • straight icing spatula
  • angled icing spatula
  • piping bags
  • Wilton 1M piping tip
  • lemon zester

Ingredients

Shortbread Crust

  • 20 Sandies shortbread cookies (11oz if using a different shortbread cookie variety)
  • 5 Tablespoons unsalted butter

Lemon Cake

  • zest 1 lemon about 1 packed Tablespoon
  • juice 1 lemon about 1/4 cup
  • 3/4 cup buttermilk room temperature
  • 2/3 cup sour cream room temperature
  • 1 Tablespoon vanilla
  • 3 whole eggs room temperature
  • 1 egg white room temperature
  • 1 teaspoon lemon extract (optional)
  • 1/3 cup vegetable oil
  • 1/4 cup all-purpose flour
  • 1 box Lemon Cake Mix (any brand will do, but I prefer Duncan Hines)

Lemon Curd Filling

  • 3 egg yolks
  • 1 whole egg
  • 3/4 cup granulated sugar
  • 1/2 cup lemon juice
  • 2 zest lemons (zest the whole lemons!)
  • 4 Tablespoons unsalted butter

Lemon Buttercream

  • 1 1/2 cup unsalted butter left out of fridge for 15 minutes or so
  • 1 teaspoon lemon extract
  • 1 Tablespoon pure vanilla you may use clear extract, but it will taste sweeter
  • 1/2 teaspoon almond extract
  • 1 pinch salt
  • 1/4 cup heavy whipping cream
  • 6-7 cups sifted powdered sugar

Garnish

  • 8-10 Sandies Cookies for garnish

Instructions

SHORTBREAD CRUST

  • In a food processor, pulse 20 Sandies, or 11oz of shortbread cookies until a powder forms.
  • Melt butter in microwave for about 30 seconds. Add to shortbread crumbles and pulse until a crust forms.
  • Divide crust between three 6" pans, 2 8" pans, or 24 cupcakes, and use the bottom of a flat measuring cup or drinking glass to make flat and even around the whole bottom. Set aside and make cake batter.

LEMON CAKE

  • Preheat the oven to 325 Convection bake or 350 Traditional bake.
  • Preheat oven to 325 degrees. Prep 3x 6 inch cake rounds with a swipe of shortening and dust of flour. Set aside.
  • In a large bowl (you do not need your stand mixer for this step), whisk together the lemon zest, lemon juice, lemon extract if using, buttermilk, sour cream, vanilla, eggs, and oil. Whisk until just combined. Sift in cake mix and flour. Split cake batter between the three cake rounds with the crust already pressed in.
  • Bake for 26-28 minutes until center is baked through (don't over-bake!). If making cupcakes, only bake for 12-15 minutes, or until cupcakes are springy in the middle. Remove from oven, let cool in pan for 5 minutes, then flip out onto a cooling rack until room temperature. Wrap and freeze overnight or freeze for at least a couple hours for easy assembly.

LEMON CURD

  • In a medium saucepan over medium heat, stir together the yolks, sugar, juice, and zest. Whisk together as the mixture begins to thicken, about 6 minutes. Curd should be thickening, and will be thick enough to coat the back of a spoon.
  • Remove curd from the heat, and stir in the butter cubes. Stir to combine until the butter has melted. Strain the curd, and discard the zest.
  • Cover the curd with a light layer of plastic wrap placed directly on top of the surface of the curd, and then store in the fridge until cooled. You’ll want it cold before adding it to your cake as filling.

LEMON BUTTERCREAM

  • In a stand mixer fitted with a paddle attachment, whip up butter for about a minute until light and fluffy. Scrape down the sides of the bowl.
  • Add in salt, lemon extract, vanilla, almond extract, and heavy cream until combined. Slowly add in powdered sugar, about a half cup at a time. Add in more heavy cream if needed for a thinner consistency. Whip on high for a minute to create a soft buttercream, then back down to low for 30 seconds to beat out any air bubbles. Reserve about 1-2 cups of buttercream and tint a soft yellow.

ASSEMBLY

  • On a cake turntable, tape a 6” cardboard round on top of a 8" cardboard round (if making a 6" cake). Add on a small amount of buttercream, spread it around to act like "glue" for holding the cake onto the board.
  • Place on first cake round, add on about a half cup of buttercream, spread it flat with an offset cake spatula. Pipe a dam around the outer rim, then spoon on about ¼ cup of lemon curd. Add on next layer, and repeat with remaining two layers.
  • Carefully crumb coat the cake, place in the fridge to set for about 10 minutes, then spread on the yellow layer on the bottom and the white buttercream on the top and top half of the cake. As shown in the video, use the straight icing spatula at a slight diagonal to swoop up the sides to create the buttercream design.
  • Mix the remaining buttercream in a 1M piping tip and pipe on swirls with Sandies cookies between each swirl. Cake slices best when cold. Enjoy!