Ingredients
1/2 cup (120 ml) fresh lemon juice
4 large egg yolks, at room temperature
3/4 cup (150 g) granulated white sugar
1/8 tsp salt
1 tbsp (10 g) lemon zest (about 1 large lemon)
1/2 cup (112 g) unsalted butter, cold and cut in cubes
2 1/4 cups (281 g) all-purpose flour, spooned and leveled
1 1/2 tsp baking powder
1/4 tsp baking soda
1/2 tsp salt
10 tbsp (140 g) unsalted butter, softened
1 1/2 cups (300 g) granulated white sugar
3 large eggs, at room temperature
1 tbsp vanilla
1 cup (240 ml) buttermilk, at room temperature
3 tbsp (30 g) lemon zest (about 3 large lemons)
3/4 cup (168 g) unsalted butter, softened
6 oz (170 g) cream cheese, cold
2 1/4 cups (293 g) powdered sugar
1/2 tbsp (5 g) lemon zest (about 1/2 large lemon)
Instructions
For the Lemon Curd
Add the lemon juice, large egg yolks, granulated white sugar, salt and lemon zest to a medium saucepan or pot. Whisk everything together.
Heat the lemon mixture over medium-low heat for 20-25 minutes, whisking frequently, until thick. It should coat the back of a spoon once thick enough.
Remove it from the heat and slowly whisk in the cold, cubbed butter.
Once all of the butter is melted in, transfer the curd to a heatproof, small bowl. Place plastic wrap on top of the curd, so it doesn't form a skin, and allow it to cool completely in the fridge.
For the Lemon Cake
Preheat the oven to 350 degrees. Spray a 9x9 pan with non-stick spray and line it with parchment paper.
In a medium bowl, whisk together the all purpose flour, baking powder, baking soda, and salt. Then set aside the flour mixture.
Add the softened butter and granulated white sugar to a large bowl. Cream together for 2 minutes with an electric mixer. (You can also use a stand mixer fit with a paddle attachment.)
Then add in the eggs and vanilla and mix on medium speed until pale in color and smooth, about 1 minute.
Add the dry ingredients and buttermilk to the wet ingredients a little at a time, mixing on low speed until the cake batter is combined. Scrape the sides of the bowl with a rubber spatula as necessary.
Fold in the lemon zest.
Pour the batter into the prepared baking pan.
Bake the cake for 35-40 minutes, or until a cake tester comes out clean from the center.
Let the cake cool in the pan on a wire rack until completely cool.
For the Lemon Cream Cheese Frosting
Add the butter to a large mixing bowl and mix on high speed with an electric mixer until pale and fluffy, about 5 minutes.(If using a stand mixer, use a whisk attachment.)
Then add in the cream cheese and mix on high speed until fluffy, about 1 minute.
Sift in the powdered sugar and mix on low speed until combined.
Add in the lemon zest, then mix on high speed until fluffy again.
Assembling the Cake
When the cake is completely cooled carefully turn the pan over to release the cake. Transfer it to a serving plate. Poke holes on the top of the cake using a wooden stick or the handle of a wooden spoon.
Transfer the lemon curd to a piping bag.
Pipe the lemon curd into the holes of the cake.
Frost the top of the cake with a thick layer of lemon cream cheese frosting using an offset spatula. Swirl lemon curd into the frosting. Then, serve!