Step 1

Preheat the oven to 350°F (180°C) and butter two 9-inch baking pans. Dust the bottom and sides with flour. Set aside.

Step 2

In the bowl of a stand mixer fitted with the whisk attachment combine the egg whites with the cream of tartar. Whisk at low speed until foamy, about 1 minute. Increase the speed to medium-high and add 1/4 cup sugar gradually. Mix until peaks are just stiff. Transfer egg whites to another bowl. Set aside.

Step 3

In the bowl of the stand mixer fitted with the paddle attachment cream together butter and sugar until pale and fluffy, about 5 minutes.

Step 4

In a small bowl sift together cake flour, baking powder, and salt.

Step 5

Add vanilla extract, poppy seeds, about 1 tbsp lemon zest, and 2-3 tbsp lemon juice to the butter mixture. Whisk until combined.

Step 6

With the mixer running on low speed add flour mixture in three batches, alternating with the milk. Beat until combined after each addition. After everything is added scrape sides of the bowl and mix for ten more seconds.

Step 7

Gently fold in the egg whites with a rubber spatula. Don't overmix!

Step 8

Divide the batter between the baking pans. Bake until the tops are golden for about 40 minutes or until a skewer inserted in the center comes out clean. Transfer to a wire rack. Cool cakes to room temperature then slice layers equally in half with a serrated knife.

Step 9

In the bowl of a stand mixer fitted with whisk attachment, cream together butter, powdered sugar, and salt on low speed until combined, scraping as necessary. Increase the speed to medium-high and beat until white and fluffy, about 2-3 minutes.

Step 10

Add cream cheese one piece at a time and mix until combined then continue to beat 2 more minutes until fluffy, scraping down the bowl as needed.

Step 11

With the mixer on, add lemon curd 1 tbsp at a time then beat another minute.

Step 12

Place first cake layer on serving platter cut-side up (reserve the flattest cake layer for the top). Spread 3 tbsp lemon curd over the top. Place second cake layer on top and spread 1/3 of the frosting over the top.

Step 13

Place third cake layer on top and spread 3 tbsp lemon curd over the top. Place final layer cut-side-down, then frost the top and sides. Reserve a little bit of the frosting to pipe onto cake as decoration.

Step 14

Store cake covered in the fridge, let come to room temperature before serving.