Leaving the skin on, use the flat grater to grate the cucumber into a mesh strainer set atop a small bowl. Once the cucumber is grated. and using a paper towel on top, begin to press down on the cucumber in the strainer to release the moisture. Empty the water in the bowl as needed and keep pushing down on the cucumber with a clean paper towel if needed, until you feel you have as much of the moisture removed from the cucumber. Set aside to let drain more while you make the sauce.
The Sauce
Measure the rest of the ingredients into a small mixing bowl. Mix to combine.
Add the grated, strained cucumber to the bowl and mix well. Taste and add kosher salt and pepper as needed.
Serving and storage
Put the Tzatziki Sauce in the fridge for at least an hour to let the flavors meld. More time in the fridge equals more melding and more flavor.
Drizzle olive oil and fresh dill on top, if desired, for serving. Serve with dolmas, lamb kafta, gluten-free crackers, and any other greek dish. Can also be used as a salad dressing and veggie dip.
Store the leftovers in the fridge for up to 3 days.