Add the sliced cucumbers, onion, and kosher salt to a large bowl. Toss to combine. Cover with plastic wrap, place in fridge, and let sit for 30 minutes.
Pour cucumber mixture into a colander set over the sink. Rinse the cucumbers and onions with water. (If you fail to rinse the cucumbers the salad will be quite salty). Let excess liquid drain out.
Place the cucumbers in a salad spinner and spin the cucumbers until mostly dry. Gently pat the cucumbers with paper towels to remove excess moisture. Place cucumbers in a large bowl.
In a small bowl whisk the Greek yogurt, sugar, dill weed, vinegar, garlic powder, and pepper. Once smooth, pour over the cucumber mixture and stir until cucumbers are covered in the dressing.
Serve immediately or cover and refrigerate until ready to serve. Best eaten the same day.
Notes
Best to eat this salad within 6 hours of making it. You don't have to peel the cucumbers. If you like cucumbers with skin on, go ahead and keep it that way, just make sure you clean the cucumbers before slicing.