01 -  Preheat oven to 300°F (150°C). Line baking sheet with parchment paper. 
 02 -  In a clean mixing bowl, beat egg whites and cream of tartar using an electric mixer until soft peaks form. Gradually sprinkle in granulated sugar while continuing to beat until stiff, glossy peaks are achieved. 
 03 -  In a separate bowl, whisk egg yolks together with cornstarch and vanilla extract until the mixture is smooth and fully incorporated. 
 04 -  Gently fold the egg yolk mixture into the whipped egg whites, maintaining volume and lightness. 
 05 -  Split batter evenly among separate bowls for each desired color. Add a few drops of gel food coloring to each bowl and carefully fold to distribute the hues. 
 06 -  Spoon colorful portions onto the prepared baking sheet, placing them side by side to form a rainbow pattern. For a marbled appearance, gently swirl the colors together with a spatula. 
 07 -  Bake in the preheated oven for 25 minutes, or until the surface is set and lightly golden. 
 08 -  Allow Cloud Bread to cool for several minutes before lifting from the baking sheet. Serve immediately for optimal fluffiness.