For the dressing toss all the ingredients together and mix well. Cover and leave overnight or in the refridgerator a few hours before adding to salad.
Salad
First make the dressing. The night before if possible.
To start, you want to thinly slice the cucumbers and the onion. You can do this with a knife or for perfect slices like you see in the photos I used this cheap vegetable slicer.
Now, salt the cucumbers heavy and toss them in a bowl and cover. Place them in the refrigerator for an hour. At the 30 minute mark pour out the excess water then place back in the fridge. With the red onion cover them in a bowl of warm water. This will soften them a bit so they aren't so raw.
When the hour hits, rinse all that excess salt from the cucumbers and give them a little pat to dry. Nothing major, you are just drying them a little from the rinsing you did. Drain the red onions as well.
In a large bowl, add the cucumbers and the red onion.
Add in the dressing and mix well. Garnish with more dill and black pepper serve immediately.