Cook and peel the hard boiled eggs if not done already.
Cut each egg in half. Scoop out the yolk into a small bowl. Set aside the egg whites.
Mash the egg yolks to your desired consistency. Add the yogurt, cucumber, dill, garlic, oil, lemon juice, and salt. Stir to combine. Season to taste with lemon, salt, dill, and yogurt to your desired flavor and consistency.
Using a piping bag or spoons, fill each egg white with the yolk mixture. Garnish if desired.
Chill until ready to serve.
Notes
If you already have tzatziki made (maybe for a veggie dip?) you can simply use 5-6 Tablespoons of prepared tzatziki instead of the listed ingredients.You can decorate the eggs with your favorite Greek salad ingredients, such as Kalamata olives, cucumber, tomatoes, feta cheese, or fresh dill.