Grate the cucumber, put into a colander, sprinkle on 1/4 teaspoon salt and allow excess water to drain.
In the meantime, stir together the yogurt, garlic, olive oil, vinegar, and remaining 1/4 teaspoon of salt in a mixing bowl. It looks like it won’t combine, but keep stirring, the olive oil will eventually disappear into the yogurt.
Place the cucumber in several paper towels or a tea towel and squeeze out any excess water. You’ll be surprised at how much water comes out.
Add the cucumber, dill, and remaining salt to the yogurt mixture and stir to combine.
Refrigerate for an hour before serving.