Shred the cucumber into a fine sieve colander and squeeze as much liquid out as possible. Sprinkle with a pinch of salt and allow to sit over the sink for 30 minutes. Squeeze out remaining liquid then add to a bowl. Mix in Greek yogurt, garlic, dill and lemon juice.
Spread the hummus in a small to medium sized serving dish, depending on how thick you want the layers. Spread the homemade tzatziki over the hummus. Sprinkle with chopped tomatoes, sliced olives and crumbled feta. Best served immediately but you can cover and refrigerate if serving later. It may get a little liquidy from the cucumbers so simply drain off as much as you can (it will still taste great).