Line an 8-inch or 9-inch square pan with one large sheet of parchment paper, covering both the bottom and sides so the cake can be lifted out easily.

Add the chopped strawberries and applesauce to a blender. Blend on high speed until completely smooth and uniform in color.

Pour the puree into a large heatproof mixing bowl. Sprinkle the gelatin evenly over the surface and whisk until fully incorporated. The mixture will become thicker.

Using a double boiler method, gently heat the mixture while stirring until the gelatin is completely dissolved. The mixture should feel warm but not hot—do not let it boil.

Remove from heat and let the mixture cool to room temperature, about 10 minutes.

Transfer the mixture to the bowl of a stand mixer fitted with the whisk attachment. Beat on the highest speed for about 15 minutes, until the mixture quadruples in volume and resembles airy whipped cream with soft peaks.

Pour the whipped mixture into the prepared pan and smooth the surface with a spatula.

Refrigerate for at least 1 hour, or until fully set.

Keep chilled until ready to serve. Slice with a large, sharp knife and serve cold.