Heat oven to 150C/130C fan/gas 2 and line 2 large baking sheets with baking paper, then grease well with butter or oil.
In a large bowl and using electric beaters, whisk the egg whites together until stiff peaks form. You should be able to carefully turn the bowl upside down without it falling out.
In another bowl, put the egg yolks, cream cheese and cream of tartar then whisk together (no need to wash the beaters first) until smooth, pale and frothy. Next, fold the egg whites, a spoonful at a time into the yolk mixture, be as gentle as you can with this so you don’t knock out too much of the air and finally fold in the nigella seeds and season with salt and pepper.
Carefully dollop the mixture onto the prepared baking sheets, if the mixture is a little runny when you get to the bottom of the bowl don’t use the last few spoonfuls – only use the really fluffy mix on the top. Bake for 20 mins or until lightly golden and craggy on top. Allow to cool for a few moments before carefully removing from the paper with a palette knife.