Peel 50 grams (1 ¾ oz) of cooked beans and turn them into a paste with a fork.
Add tahini, vinegar, olive oil, lemon juice, and salt then whisk.
Add water if the sauce is too thick, check the seasoning and add more salt if needed.
Assembling the Piyaz
In a bowl, put the rest of the beans, sliced onions, parsley, chili flakes if using, paprika, freshly ground black pepper and salt.
Add the sauce to the salad and give it a gentle stir just enough to combine.
Put in a serving bowl or individual bowls, and garnish with hard-boiled eggs and chopped tomatoes.
Notes
Use high-quality ingredients. Since Piyaz is a simple salad, the quality of the ingredients is important. Choose fresh vegetables and herbs for the best flavor and texture.
Red onions have a strong flavor and can be bitter sometimes. This recipe requires plenty of raw red onions and you might want to mellow out their pungent flavor. Simply rub them with salt, lemon juice, and a bit of sumac to soften them and make them much more palatable.
This salad tastes better when served freshly made. If you want to make it ahead, don't add the dressing and the garnishes to the salad, and keep them in a separate container.
Taste the salad before serving and adjust the seasoning if necessary. Add more salt, pepper, or vinegar if needed to enhance the flavor.
You can keep this salad refrigerated in an airtight container for up to 3 days. I don't recommend freezing Piyaz Salad.