Ultimate Lemon Layer Cake

Directions

1. 1
   Filling: Measure 1 tablespoon lemon juice into a small bowl; sprinkle gelatin over the top.
2. 2
   Heat remaining lemon juice, sugar, and salt in medium non-reactive sauce pan over medium high heat, stirring occasionally until sugar dissolves and mixture is hot, but not boiling.
3. 3
   Whisk eggs and yolks in a large non-reactive bowl.
4. 4
   Whisking constantly, slowly pour hot lemon-sugar mixture into eggs, then return mixture to saucepan.
5. 5
   Cook over medium-low heat, stirring constantly until mixture reaches 170° and is thick enought to leave a trail when a spatula is scraped along the bottom of the pan, about 4-6 minutes.
6. 6
   Immediately remove pan from heat and stir in gelatin mixture until dissolved. Stir in frozen butter until incorporated.
7. 7
   Pour filling through a fine-meshed strainer into a bowl.
8. 8
   Cover surface with plastic wrap; refrigerate until firm enough to spread, about 4 hours.
9. 9
   Cake: Preheat oven to 350°.
10. 10
    Grease and flour two 9-inch cake pans and line with parchment paper.
11. 11
    In a medium bowl, whisk together egg milk, egg whites and vanilla.
12. 12
    In a mixer bowl, combine flour, sugar, baking powder and salt; mix at slow speed.
13. 13
    Add butter one piece at a time, continue to beat until mixture resembles moist crumbs and no visible butter chunks.
14. 14
    Add all but 1 cup of milk mixture to crumbs and beat at medium speed until mixture is pale and fluffy, about 1 1/2 minutes.
15. 15
    With mixer running, add remaining 1/2 cup milk mixture, beat 1 mintute more.
16. 16
    Divide batter evenly between cake pans.
17. 17
    Bake 23-25 minutes or until toothpick in center of cakes comes out clean.
18. 18
    Loosen cakes from side of pan with a small knife, cool in pan 10 minutes then remove from pan onto greased wire rack, remove parchment paper, invert again and cool completely.
19. 19
    Icing: Combine all ingredients in a mixer bowl or heatproof bowl.
20. 20
    Set over medium saucepan filled with 1-inch of simmering water.
21. 21
    Cook stirring constantly until mixture reaches 160°, 5-10 minutes.
22. 22
    Transfer mixture to mixer bowl (if needed) and beat on medium speed until soft peaks form, about 5 minutes.
23. 23
    Increase speed to medium-high and continue to beat until mixture has cooled to room temperature and stiff peaks form, about 5 minutes longer.
24. 24
    Assembly: Cut each layer in half horizontally.
25. 25
    Spread 1 cup of lemon filling evenly on each cake, (except the top layer) leaving 1/2-inch border around cake.
26. 26
    Place top layer on cakes, smooth out any filling that may have leaked from the layers.
27. 27
    Refrigerate while you make the icing.
28. 28
    Spread icing on cake.