Heat oven to 300° F.

Lightly coat large baking sheet with spray. Set aside.

Separate egg yolks from egg whites. Place whites in a medium bowl. Place yolks in a separate medium bowl. Set aside.

Add cream of tartar to egg whites. Beat with a mixer on high until stiff peaks form, about 4 minutes. Set aside.

Add salt and yogurt to egg yolks. Beat with a mixer on medium until blended.

Gently fold ⅓ of egg white mixture into egg yolk mixture. Fold in the remaining egg white mixture until just incorporated, being careful not to overmix.

Using a spoon, transfer a scoop of egg mixture onto prepared baking sheet, gently spreading into a thick pancake shape about 3 inches in diameter. Repeat with remaining batter.

Bake for 25 to 30 minutes, or until golden brown and exterior is crispy to the touch. Immediately loosen cloud breads with a spatula; allow to cool on the baking sheet for 3 minutes, then transfer to a wire rack to cool completely.

Serve immediately, or store in an airtight container.