Line a baking pan and preheat your oven to 325F. You'll also need to sift the dry ingredients (besides the sugar) and set them aside.
Add the egg whites and cream of tartar to a bowl. Beat until you have soft peaks. Gradually add 1/2 of the Splenda, until it begins to look fluffy.
In a separate bowl, add the rest of the Splenda, egg yolks, water, and extract. Mix well and then add to the bowl of sifted dry ingredients. Now add the final bowl of egg whites to your main bowl and keep mixing until just combined.
Pour your batter into your prepared cake pan and bake in the center of your oven for around 55-60 minutes. Leave to cool before frosting. Slice, serve, and enjoy!