In a small bowl combine the sliced onion with 1 tablespoon lemon juice and 1 tablespoon olive oil. Season with salt and pepper to taste. Set aside.
In a separate small bowl combine the feta, olives and 1 tablespoon olive oil and smash lightly with a fork until blended.
Divide the feta mixture between 4 slices of bread. Scatter the Pepperoncini peppers on top of the feta.
Top with the sliced cucumber, tomato and onion. Drizzle the onion marinade on the 4 remaining slices of bread and spread with hummus. Season with salt and pepper and fold both sides together.
Notes
Sandwich may be made ahead, wrapped tightly in plastic wrap and served within 24 hours. Keep refrigerated or in a cooler until ready to serve. Great for picnics!
Nutrition information is calculated using an ingredient database and should be considered an estimate. When multiple ingredient alternatives are given, the first listed is calculated for nutrition. Garnishes and optional ingredients are not included.