Peel the cucumber and cut in half lengthwise. Use a spoon to remove the seeds. Grate the cucumber using a box grater. Alternatively, you can finely chop the cucumber.
Place the grated cucumber in a fine mesh sieve over a bowl and sprinkle with kosher salt. Let it sit for about 30 minutes to remove excess moisture. Use your hands to squeeze out any remaining moisture from the cucumber then pat it dry with a paper towel.
In a mixing bowl, combine the Greek yogurt, sour cream, lemon juice, chopped dill, and minced garlic. Mix well until all ingredients are thoroughly combined.
Then, add the grated cucumber to the yogurt mixture and stir until evenly combined.
Taste and season with salt and pepper. The flavors of the tzatziki will develop further as it sits. Enjoy immediately or cover and refrigerate until ready to use.
Notes
Consider straining the sour cream and yogurt before using to remove any excess liquid. To do so, place the yogurt and sour cream in a fine mesh sieve sitting over a bowl and refrigerate for two hours.
Be sure to take the time to remove the moisture from the cucumber before using otherwise you'll end up with watery tzatziki.
This easy homemade tzatziki sauce with sour cream is great served as a dip with fresh veggies or pita chips. You can also use it as a salad dressing or spread for chicken gyros.
Store leftover tzatziki in an airtight container in the refrigerator for up to five days. Stir before using.