Preheat oven to 375 degrees. Coat eight 4-ounce ramekins with vegetable cooking spray and sprinkle a little Splenda inside each – like flouring a cake pan. Set on a baking sheet.
In a large bowl whisk the yogurt with the egg yolks, 1/3 cup Splenda, flour, vanilla, lemon, and salt until smooth.
In another bowl beat the egg whites and cream of tartar with an electric mixer until foamy. Add in the 2 tablespoons of Splenda and continue beating until very stiff peaks form. (When you pull the beaters straight up out of the whites the peaks stand up and don’t curl.) Carefully fold the whites into the yogurt mixture until no puffs remain.
Divide among the ramekins and bake for 15 minutes or until just golden and set. Serving immediately they will be souffle-like. Chilled they will be more cheesecakey.