Wash the English cucumbers and dice them into small pieces. Place in a colander, sprinkle with salt, and let sit for 10-15 minutes.

In a mixing bowl, combine yogurt, crumbled feta, herbs, lemon zest, juice, and pepper. Stir until well blended.

After draining, pat cucumbers dry with a paper towel. Add to yogurt mixture and fold gently.

Toast the bread slices until golden brown. On one slice, layer sprouts, then add cucumber salad mixture. Top with onion and another slice of bread.

Cut the sandwiches in half and serve immediately for the best texture and flavor.