Place cucumbers and onions in a large bowl. Set aside.
In a small bowl, add sour cream, olive oil, vinegar, sugar, garlic powder, salt and pepper. Whisk together. Pour over cucumbers and onions. Sprinkle on chopped dill and toss together. Cover and chill in refrigerator up to 30 minutes. When ready to serve, toss again, and sprinkle on more dill if desired. Serve immediately!