Method

1. For the filling: Combine 1 tablespoon lemon juice with gelatin.
2. In a saucepan heat remaining lemon juice, Natvia, and salt over medium-high heat, stir until mixture is hot but not boiling. In a separate bowl whisk eggs and yolks together. Slowly pour the lemon mixture in saucepan into the eggs. Transfer back the mixture into the saucepan and cook for 4-5 minutes.
3. Remove from heat and stir in gelatin mixture until dissolved followed by butter and mix until well combined. Strain through a mesh filter to remove any grain or solids from the mix. Refrigerate until firm.
4. For the cake: preheat oven to 180C. Grease and line two 20 cm cake pans.
5. Whisk together egg whites and vanilla extract. In another bowl combine flour, Natvia, baking powder and salt, mix with a beater at low speed. Add butter cubes one piece at a time, continue to beat until mixture resembles moist crumbs.
6. Add all ingredients except milk to crumbs and beat at medium speed until mixture is pale and fluffy. Add milk and continue mixing.
7. Transfer the mix into the cake pan and separate evenly. Bake 23-25 minutes or until a toothpick comes out clean.
8. Cool cakes in pan before transferring to wire rack to cool completely
9. For the icing: Combine all ingredients in a bowl. Cook and stir over a saucepan with boiling water for 5-10 minutes. Remove from heat and beat until soft peaks form. Continue beating until stiff peaks form.
10. To assemble the cake cut each cake in half horizontally to create 4 layers. Spread 1 cup of lemon filling evenly on each cake, or until the cake is evenly covered with lemon curd. Place the layers on top until you have 4 layers of cake with fillings in between, smooth out any filling that may have leaked from the layers.
11. Refrigerate while you make the icing and spread icing on cake.