2 cups cherry tomatoes (multicolored if you’ve got ‘em), halved
1 medium bunch curly parsley, rinsed, dried well, and finely chopped
¾ cup finely diced red onion
Place the quinoa in a bowl, cover with cold water, rub it around with your fingers, and drain out the water (this removes any soapy flavor quinoa can sometimes have). Bring a medium pot of water and the quinoa to a boil, turn it down to a simmer, cook until tender but not mushy, about 10 minutes. Drain well, then spread it out on a sheet pan to cool (this also helps dry out the quinoa).
Stack the mint leaves onto one another, with the largest ones on the bottom, and roll them into a log. Using the sharpest knife you have, cut the mint into thin strips.
Whisk the lemon juice, olive oil, sumac, and salt in a large bowl. Add the quinoa, tomatoes, parsley, onions, and sliced mint and toss to coat. Refrigerate for 30 minutes, then season to taste with more lemon juice and salt to taste.