Preheat your oven to 300°F (150°C) and line a loaf pan with parchment paper.

Carefully separate the egg whites and yolks into two clean bowls, ensuring that no yolk touches the whites.

Add cream of tartar to the egg whites and beat with an electric mixer on high speed until stiff peaks form, about 3-5 minutes.

In the bowl with the egg yolks, combine the cream cheese and salt, then beat until smooth and creamy, about 2-3 minutes.

Gently fold the whipped egg whites into the yolk and cream cheese mixture in batches.

Divide the batter into several bowls and add a few drops of gel food coloring to each bowl, mixing until desired shades are achieved.

Spoon the colored batters in alternating blobs into the prepared loaf pan and use a skewer to swirl the colors.

Bake for 30-40 minutes until the top is lightly golden and springy to the touch.

Allow the loaf to cool in the pan for about 5-10 minutes before carefully removing and cooling completely on a wire rack.