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.

Remove it from the heat and slowly whisk in the cold, cubed butter.

Transfer the curd to a heatproof bowl, cover with plastic wrap, and allow it to cool completely in the fridge.

Preheat the oven to 350 degrees. Spray a 9×9 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. Set aside.

In a large bowl, cream together the softened butter and granulated white sugar for 2 minutes with an electric mixer.

Add in the eggs and vanilla, mixing on medium speed until pale and smooth.

Add the dry ingredients and buttermilk to the wet ingredients gradually, mixing on low speed until combined.

Fold in the lemon zest.

Pour the batter into the prepared baking pan.

Bake for 35-40 minutes or until a cake tester comes out clean.

Let the cake cool in the pan on a wire rack until completely cool.

Add the softened butter to a mixing bowl and beat on high speed until pale and fluffy.

Add in the cold cream cheese and mix on high speed until fluffy.

Sift in the powdered sugar and mix on low speed until combined.

Add in the lemon zest and mix on high speed until fluffy again.

Once the cake is completely cooled, carefully turn the pan over to release the cake.

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 and pipe it into the holes of the cake.

Frost the top of the cake with a thick layer of lemon cream cheese frosting.

Swirl lemon curd into the frosting and serve!