Grate the cucumber using the large holes of a box grater. Keeping the skin on adds texture and color to your tzatziki.
Squeeze out the moisture from the grated cucumber using a clean kitchen towel or paper towels until barely any liquid remains. This prevents the sauce from becoming watery.
In a medium bowl, stir together the drained cucumber, Greek yogurt, lemon juice, olive oil, garlic, salt, dill, and mint if using. Mix until everything is smooth and evenly combined.
Chill the sauce in the fridge for 30 minutes before serving to allow the flavors to meld. While this step is optional, it is highly recommended for the best flavor.
Notes
Use fresh ingredients for the best taste.
Tzatziki sauce can be made a day in advance and stored in an airtight container.
Serve it with grilled meats, pita bread, or fresh vegetables.