Preheat oven to 325 degrees. Line three ungreased 8-inch or 9-inch cake pans with a round of parchment paper.  I used 9-inch pans, but if you prefer thicker layers, use the 8-inch.

 Cake

1. Measure and sift the cake flour into a medium bowl. In a large bowl, measure and resift the cake flour along with the sugar, baking powder, and salt.
2. Zest and juice the lemons, reserving 2 tablespoons of zest and 1/4 cup of lemon juice.
3. Separate the eggs, adding the yolks to a small bowl and the whites to the large bowl of a stand mixer.
4. Make a well in the center of the flour mixture. Add the oil, egg yolks, water, vanilla, lemon zest and juice. Whisk together until well combined. Set aside.
5. Add the cream of tartar to the egg whites. Using the whisk attachment, whisk the egg whites on high speed until stiff peaks form, about two minutes.
6. Add the egg yolk mixture to the egg whites and gently fold the whites into the egg yolk mixture using a spatula. Don’t worry if you see little lumps of egg white. It doesn’t have to be totally mixed in.
7. Pour batter into the prepared cake pans. Bake approximately 35 to 40 minutes until the cakes spring back when lightly touched.
8. Once the cakes are baked, transfer them to a wire rack to cool completely.  Once they have cooled, run a sharp knife around the edges to loosen cakes and invert them onto the wire rack.  Peel off the parchment paper.

Lemon Curd Filling

1. Place one cake layer on a cake plate.  Spread 1/2 cup of the lemon curd over the cake layer.  Place a second cake layer on top of the lemon curd and spread the remaining 1/2 cup of lemon curd over it.  Top with the third cake layer and finish cake with the frosting of your choice.

Lemon Buttercream Frosting (option 1)

1. Cream the butter in a mixing bowl with an electric mixer. Add the lemon zest, sugar, and the lemon juice, one tablespoon at a time. Mix until smooth and creamy. Spread over top and sides of cake.
2. Garnish the top of the cake with extra zest if desired.

Lemon Whipped Cream Frosting (option 2)

1. Add the whipping cream to the bowl of a stand mixer fitted with the whisk attachment.  Cover mixer with an old kitchen towel to prevent splattering.  Beat on high speed until the whipped cream becomes thick, about 1 minute.
2. Add the sugar and lemon curd and mix on medium-low speed to combine.  Refrigerate until ready to use.
3. Spread the frosting over the top and sides of the cake.
4. Refrigerate cake until ready to serve.