Grate the cucumber using a box grater or food processor. Place the grated cucumber in a clean kitchen towel or cheesecloth and squeeze out as much excess water as possible. This step prevents the tzatziki from becoming too watery.
In a bowl, mix together the Greek yogurt, grated cucumber, minced garlic, lemon juice, and olive oil. Stir well to combine.
Add the fresh dill (or mint), salt, and pepper. Taste and adjust the seasoning if needed.
Let the tzatziki sit in the fridge for at least 10 minutes before serving to allow the flavors to meld. You can also make it ahead of time and refrigerate for up to 24 hours.
Serve chilled with pita bread, vegetable sticks, or as a sauce for grilled meats like lamb or chicken.
