Preheat oven to 350 degrees F.
In a large bowl, combine flour, baking powder, salt, and 1/2 cup sugar.
Add oil, egg yolks, water and lemon rind.
Beat with an electric mixer until smooth.
In a small bowl, beat egg whites and cream of tartar until peaks form.
Slowly add 3/4 cup sugar, and beat until stiff peaks form.
Fold 1/3 of the whites into the batter, then quickly fold in remaining whites until no streaks remain.
Turn batter into ungreased 10 inch tube pan. Bake at 350 degrees-F for 60 minutes or until a toothpick inserted in the center comes out clean.
Invert cake and cool completely in pan. When cool, loosen edges to remove cake from the pan.
To make filling, beat cream to stiff peaks. Fold in lemon filling.
Chill until stiff.
To assemble cake:
Slice cake horizontally into 3 equal layers. Fill layers with 1/3 cup of filling.
Spread remaining filling on top layer.
Decorate with lemon slices.
Not a NESTLÉ®-tested recipe.