Wash and dice the English cucumbers into small pieces. Sprinkle a pinch of salt and transfer to a colander. Allow sitting for 15 minutes.

In a mixing bowl, combine yogurt, crumbled feta, chopped herbs, lemon zest, lemon juice, and black pepper until smooth.

After draining cucumbers, press them with a paper towel to remove excess moisture, then add to the yogurt mixture.

Fold the drained cucumbers into the yogurt mixture with a spatula until well combined.

Assemble sandwiches by spreading sprouts on one slice of toast, adding cucumber mixture, and topping with onion, then closing with another slice.

Slice sandwiches in half for serving and enjoy fresh.