Before you begin, preheat your oven to 300 degrees. I use a silpat baking mat on top of my cookie sheet, but parchment paper works too.
Mix together egg yolks (yolks only) and Greek yogurt until blended smooth. I'd almost say overblend these, try to get rid of as many lumps as you can.
Beat egg whites and ¼ teaspoon baking powder (some have used cream of tartar instead) until fluffy. Again, I'd overblend these and make sure to get the same consistency from top to bottom of your bowl.
Fold the egg white mixture into the yolk and Greek yogurt mixture carefully. Be careful not to overmix, but know that these need to be fully mixed for your cloud bread to come out fluffy and beautiful. I recommend using a large whisk of some kind to do this.
Using a cookie scooper, take a scoopful of batter out of the bowl and tap it a few times lightly on the counter to let the big air bubbles out before baking. Drop the batter on your silpat baking mat, leaving a little room in between.
Bake for 25 minutes at 300 degrees, or until golden brown. Sprinkle sea salt on the cloud bread as soon as they come out of the oven, then move to a cooling rack.
If your cloud bread comes out runny or flat, it's because either the egg whites weren't stiff enough or you mixed too long and flattened the egg whites. The puffy texture is all because of the egg whites.
The most common issue people run into making cloud bread with Greek yogurt is that they're flat. Like I mentioned above, it's all about how stiff your egg whites are and how much you mix your batter.
Sprinkle anything you want on cloud bread when it comes out of the oven–Italian spices, salt, garlic powder, etc.
This is not the recipe to swap ingredients in–each of the three ingredients has a place in the recipe and should not be swapped for other foods.
It is important that the eggs are room temperature–not warmed in a bowl of warm water or the microwave, but true room temperature. I leave mine out for at least 3 hours on the counter. I think this helps the cloud bread batter turn out fluffy and not runny. I also pull out my Greek yogurt before, but not necessarily 3 hours before.