Use a large sheet of parchment paper to line the sides and bottom of an 8 inch or 9 inch square pan. You want to use a single sheet so that you can lift the cake out of the pan after.

Add strawberries and applesauce to a blender. Blend on high speed until strawberries are fully pureed and the puree is uniform in color.

Add puree to a large heat-proof mixing bowl. Sprinkle gelatin across the surface. Whisk until gelatin is fully incorporated. The gelatin powder should make your puree thicker and chunkier.

Using the double boiler method on the stove, dissolve the gelatin completely. When the gelatin is dissolved, your mixture should become thinner and more liquidy. The mixture should feel warm to the touch, but not hot. Be careful to not let the mixture get hot or boil. Remove bowl from stove and let it sit on the counter for about 10 minutes to cool the mixture back to room temperature.

Pour mixture into the bowl of a stand mixer. Using the wire whisk attachment, beat on highest speed for about 15 minutes. Your mixture should quadruple in volume and should look like airy whipped cream. When you stop your mixer, your wire whisk should be able to hold a soft peak.

Pour mixture into your prepared pan. Use a spatula to spread it evenly across and smooth the surface. Place into fridge for at least 1 hour to set.

Keep the cake in the fridge until ready to serve. Before serving, you can decorate the cake with whipped cream frosting or other frosting. Slice cake with a very large and sharp knife. The cake is best served chilled. Store any uneaten cake in the fridge.