Preheat the oven to 300°F (150°C). Line a baking sheet with parchment paper and lightly coat it with nonstick spray.
In a medium bowl, beat the egg whites with cream of tartar using a hand mixer until stiff peaks form. Set aside.
In a separate bowl, whisk together the egg yolks, Greek yogurt, and sea salt until smooth and pale.
Gently fold the whipped egg whites into the yolk mixture, one-third at a time. Use a spatula and fold slowly to keep the mixture airy.
Scoop the batter into 6–8 round mounds on the prepared baking sheet, flattening slightly with the back of a spoon.
Bake for 25–30 minutes or until golden and set.
Remove from the oven and let cool for 5 minutes. Serve warm or allow to cool completely before storing.