Toss the thinly sliced cucumbers with 0.3 teaspoon sea salt in a colander and let them rest over a bowl for 10 minutes to drain excess liquid.

Whisk together the Greek yogurt, mayonnaise, fresh lemon juice, lemon zest, fresh dill, garlic powder, remaining salt, and cracked black pepper in a small bowl until smooth.

Pat the drained cucumbers dry with a paper towel and transfer them to a wide mixing bowl alongside the shaved red onion and drained capers.

Pour the creamy dressing over the cucumber mixture and toss gently until evenly coated.

Fold in the flaked smoked salmon gently to keep large, tender pieces intact, then transfer to a chilled platter to serve.