01 - Preheat oven to 300°F. Line baking sheet with parchment paper.
02 - Beat egg whites and cream of tartar in a large bowl until soft peaks form. Gradually add sugar, beating until stiff and glossy.
03 - Whisk egg yolks together with cornstarch and vanilla extract until fully blended.
04 - Gently fold the yolk mixture into whipped egg whites, maintaining aeration and volume.
05 - Divide batter evenly into bowls, add desired food coloring, and fold gently to achieve vibrant hues.
06 - Spoon colorful mixtures onto prepared baking sheet side by side for rainbow effect. Swirl gently with spatula for marbled appearance.
07 - Transfer to oven and bake for 25 minutes until set and lightly golden.
08 - Allow bread to cool briefly before removing from baking sheet. Serve immediately for optimal texture.