Preheat oven to 275°F. Line a large cookie sheet with parchment paper.
In a standing mixer fitted with the whisk attachment, whip the egg whites on high speed until light and foamy. Slowly add in sugar, cream of tartar, and salt, and continue to whip until stiff peaks form and the sugar granules absorb completely.
Heat the nutella in a microwave-safe bowl for 30 seconds, then stir. It should be completely liquified, but if not, nuke it for another 15 seconds.
Scoop 1 large spoonful of nutella over the meringue. Do not fold it in.
Use a large cookie scoop to scoop out the meringue onto the lined cookie sheet. Clean your scoop between each scoop. Drizzle a small amount of nutella over each cookie. Swirl the back of a clean spoon in a circular motion on the top of the cookie to flatten it slightly and swirl the nutella.
Bake the cookies for 1 hour, then allow to cool completely before serving.