Shred cucumber with a grater. Place in a towel and squeeze as much moisture out as possible.
Combine the cucumber and remaining ingredients in a medium bowl.
Mix until fully combined and refrigerate until ready to serve.
Notes
Tzatziki is best served cold!
Refrigerate tzatziki for up to two days.
Caution! If stored longer, there is a risk that the garlic, which has extremely low acidity, may produce botulism, a serious toxin, and that is not a risk worth taking.
Avoid freezing this sauce as it may become watery.