In a medium bowl, mix together with a whisk or wooden spoon, yogurt, sour cream, egg, salt, baking soda, baking powder and sugar. Add flour and vanilla.
Grease or spray a 3 - 9" layer pans and divide batter evenly between pans. (the batter will seem skimpy....but spread as evenly as you can with a spatula in each pan - layers will rise on baking).
Bake at 350 for only 10-12 minutes.
Cool on racks and remove from pans with a plastic spatula onto racks to finish cooling as soon as you can handle the cakes.
IMPORTANT: Do NOT over bake! If not using immediately - put wax paper between layers, cover with plastic and refrigerate or freeze till ready to assemble cake.
Layer cake layers: 1/3 whipped cream and 1/2 sweetened sliced strawberries, or fruit of choice - then 1/3 whipped cream and 1/2 berries. Last layer - just whipped cream. Decorate with berries.
This cake tastes even better the next day and the day after that... if there is any left! The Trick is not over baking the layers or it will be dry and not nice and moist.