01 - Preheat the oven to 300°F. Line a baking sheet with parchment paper to prevent sticking.
02 - Using a clean mixing bowl and mixer, beat egg whites and cream of tartar on high speed until soft peaks form. Gradually add sugar and continue beating until stiff, glossy peaks are achieved.
03 - In another bowl, whisk egg yolks, cornstarch, and vanilla extract until homogeneous and smooth.
04 - Carefully fold the egg yolk mixture into the whipped egg whites, blending gently to maintain maximum aeration.
05 - Divide the batter into four equal portions. Into each bowl, add a few drops of your chosen gel food coloring and fold gently until color is evenly distributed.
06 - Spoon each colored batter side by side onto the prepared baking sheet. Create a rainbow pattern, swirling gently with a spatula for a marbled aesthetic if desired.
07 - Transfer to the oven and bake for 25 minutes, or until cloud bread is set and edges are lightly golden.
08 - Let cool for several minutes before lifting from the baking sheet. Serve immediately for optimal fluffiness.