Transfer red onion slices to a medium bowl and toss with the sumac, chile flakes, salt and pepper. Massage the spices into the onion with your hands to soften and set aside.

Slice the cherry tomatoes in half or use de-seeded chopped tomatoes. Add them to bowl with onions along with the parsley, lemon juice, olive oil and beans tossing to combine with spoon.

Serve with grilled meats, flat bread or sprinkled with crumbled feta cheese as a side salad.