Chop cucumber and tomatoes into bite size pieces. Place in a large salad bowl.
Add chopped red onion and garlic, if using. Add parsley.
In a measuring cup, whisk together sour cream, lemon juice, salt, pepper and dill. Pour over vegetables.
Gently toss to coat.
Serve salad immediately or cover bowl with plastic wrap and chill in fridge until ready to serve.
Notes
You can use any cucumbers you have on hand. You can peel the skin off, especially if it's thick and waxy. I like to use Roma tomatoes in salads because they are firmer and won't mush. You can use grape tomatoes as well.