01 - Preheat oven to 300°F. Line a baking sheet with parchment paper.
02 - In a clean mixing bowl, beat egg whites with cream of tartar using an electric mixer until soft peaks form. Gradually add granulated sugar, beating until stiff, glossy peaks develop.
03 - In a separate bowl, whisk together egg yolks, cornstarch, and vanilla extract until smooth.
04 - Gently fold the egg yolk mixture into the whipped egg whites, maintaining the fluffy structure.
05 - Divide batter evenly into several bowls based on number of colors desired. Add a few drops of gel food coloring to each bowl and gently fold to integrate the hues.
06 - Spoon colorful portions onto prepared baking sheet side by side for a rainbow effect. Optionally, swirl gently with a spatula for a marbled presentation.
07 - Bake for 25 minutes, until set and lightly golden.
08 - Allow to cool for several minutes before removing from baking sheet. Serve immediately for optimal fluffiness.