Prepare Cucumbers: Wash and dice English cucumbers into small pieces. Sprinkle salt over diced cucumbers and let sit in a colander for 15 minutes.

Make Yogurt Mixture: In a mixing bowl, combine yogurt, feta, herbs, lemon zest, lemon juice, and pepper. Stir until smooth.

Drain Cucumbers: After 15 minutes, pat the cucumbers dry with paper towels to remove excess moisture.

Combine Mixtures: Add drained cucumber to the yogurt mixture and fold gently until coated.

Assemble Sandwiches: Layer sprouts on bread, add cucumber mixture, top with onion slices, and close with another bread slice.

Serve Immediately: Slice sandwiches in half and serve fresh for best texture.