Turn the oven up to 300 F and line a baking sheet with parchment paper.

In a big bowl, beat the egg whites with the cream of tartar until stiff peaks form. In another bowl, stir together the mashed avocado and egg yolks, then gently fold that mix into the egg white mix.

Drop 1/4 cups of the mix onto the baking sheet, keeping them about an inch apart. Smooth them out and sprinkle them evenly with bagel seasoning

Bake the sheet in the preheated oven until bottoms start to brown and tops are firm to the touch, 30 to 35 minutes. Let the cakes rest for at least 30 minutes, then carefully remove them from the pan with a spatula.