Preheat the oven to 325 degrees F. Lightly spray two 9-inch round cake pans or a 10-inch tube pan with cooking spray. Dust with flour.
In a large bowl, sift together cake flour, fructose, baking powder, and salt. Make a well in the middle.
Beat together oil, egg yolks, egg substitute, water, vanilla, and lemon zest. Pour into flour mixture; blend well.
In a large mxing bowl, beat egg whites until frothy. Add cream of tartar and beat until egg whites form stiff peaks.
Stir about 1/2 cup beaten egg whites into flour and egg mixture to lighten it. Gently fold in the remaining egg whites. When blended, divide batter between prepared cake pans. Bake for 25 to 30 minutes (50 to 55 minutes for tube pan), until cake is golden brown and begins to pull away slightly from the sides. Do NOT open the oven door until cake is almost done, or it may fall. Run metal spatula or knife around the edges and turn out at once onto a wire rack. Cool completely.