Into a medium sauce pot with a lid, place a steamer basket, or you can use a double boiler. Add enough water to come up about 1” below the steamer basket. Bring the water to a boil.
Add the eggs and lower the heat to a medium/gentle simmer. Place the lid on the top of the pot.
Set your timer for 14 minutes. (Overcooking eggs is what causes the greyish halo around the yolks. We are definitely trying to avoid that. It may take a round or two for you to find the perfect number of minutes, due to your heat source, boil rate, size of eggs, etc.
While the eggs are steaming, fill a medium-sized bowl with ice and water.
After 14 minutes, turn the heat off and CAREFULLY remove the lid.
Using a slotted spoon, remove the eggs from the pot and gently place them into the ice water.
Allow the eggs to cool in the ice water for at least 15 minutes, adding more ice as necessary to keep the water very cold.
Make the filling. Once the eggs are cooled, peel them. Run them under water to be sure you’re not missing any tiny pieces of shell stuck to the egg.
Halve all the eggs longways. Gently scoop the yolks of all the eggs into a medium bowl. My small teaspoons work well to pop the yolk out of the white. Mash the yolks with a fork until almost smooth.
Add the mayonnaise or Greek yogurt, oregano or dill, lemon juice, garlic powder, onion powder, salt and pepper as desired. Gently combine the ingredients. Taste for seasoning and adjust. (Keep tasting and adjusting until you get the right amount of salt and pop from the lemon.) The mixture should be stiff enough to pipe the filling with a large frosting tip, but you can spoon the filling into the egg white if you prefer.
Evenly divide the mixture by filling/piping the yolk filling into the empty “holes” in the egg whites.
Sprinkle the tops with sumac and chives just before serving. The sumac will darken as it sits. Be aware of this. You may want to opt for sprinkling with paprika if you’re going to be traveling with the eggs or they’ll be sitting on a table for a couple of hours. Sumac is a traditional Grecian spice, but a little persnickety.
Serve immediately or cover and refrigerate until ready to serve. Deviled eggs should keep well for up to 1 week in an airtight container. See Notes.