Spoon the yogurt into a large coffee filter or a cheesecloth-lined strainer; set over a bowl and let stand in the refrigerator for 2 hours or overnight. Discard the liquid. The solids that remain are the "yogurt cheese."
Combine the yogurt cheese, cucumber, garlic, oil, dill, lemon juice and salt in a bowl. Mix well and enjoy!
Notes
You can start a day ahead to make the yogurt cheese. The longer it can drain, the richer the flavor.
The flavor in Tzatziki sauce improves with time. Try refrigerating it a day or two before serving so that the ingredients have a chance to blend.
Serve with grilled pork, lamb or other meats, or as an appetizer dip with fresh vegetables for dunking.