Spray a 10x15" jelly roll pan with non-stick cooking spray or line with parchment paper. Set aside.
In a bowl, whisk together flour, baking powder and salt. Set aside.
In another bowl beat your egg whites (using a hand or stand mixer) until foamy. Then gradually add in 1/2 cup sugar and continue beating until stiff peaks form.
In another bowl beat your egg yolks together with your remaining sugar until it starts to thicken.
Slowly beat in your flour mixture (this will be stiff). Mix just until combined, scraping the sides of the bowl as needed.
Stir in about 1 cup of egg whites to loosen the mixture up a bit then fold in remaining egg whites. Fold until completely blended, but be sure to do it gently.
Spread onto prepared pan and bake for about 13-15 minutes or until top springs back when touched.
Set aside to cool completely.
Once the cake is cool, spread strawberry preserves (use as much as you'd like) over the top of cake. Then spread your whipped topping over the top of that.
Sprinkle with diced strawberries.
Store in the refrigerator.
The calories shown are based on the cake being cut into 20 pieces, with 1 serving being 1 slice of cake. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate. **We are not dietitians and recommend you seek a nutritionist for exact nutritional information.**