In a medium bowl, toss together the cucumbers, tomatoes, onion, and radishes.
Add the olive oil, lemon juice, and salt and toss to coat well.
Season with more salt, if needed.
Divide the hummus between two serving plates and make a well in the center.
Fill the inside of each with half of the tahini and top with half of the chopped salad.
Finish with a little olive oil and a juicy pinch of sumac.
