Season the chicken pieces with Ras El Hanout (or shawarma seasoning), paprika, salt, and pepper. (if using shawarma seasoning do not add the paprika)
Heat a non-stick pan over medium-high heat. Add oil and sliced white onion; sauté until translucent.
Add chicken and cook until golden brown and cooked through. About 6-8 minutes. Set aside on a plate. (This step can be made ahead)
Prepare quinoa, using a fine-mesh strainer, rinse the quinoa under cold running water.
Rub and swish the quinoa with your hands while rinsing to remove the natural coating. At first, the water will be whiteish, but as you let it run, it will get clear. Drain the quinoa and place it into a pot.
Add 1.5 cups of water, about 2/3 tsp of kosher salt, and set the heat to high. Boil until liquid is cooked off and 'tails' are visible about 12-15 minutes.
While the quinoa is cooking prepare the salad, chop the onion, bell pepper, cucumber, tomatoes, and parsley. Combine chopped onion, bell pepper, cucumber, and cherry tomatoes to a bowl.
Add lemon juice, olive oil, a pinch of salt and ground pepper; toss well to combine. Garnish with chopped parsley and set aside.
When the quinoa is done, fluff with a fork and allow it to cool.
For assembling, add quinoa to the serving bowls.
Top each serving with chicken shawarma. Add the salad next to it and serve.
OPTIONAL: drizzle a bit of lemon juice over the chicken shawarma