To make these kebabs, start by preheating your oven to 375°F.
Add the chopped bell pepper, onion, garlic, and parsley to a small food processor and blend until the mixture is fairly liquidy.
Transfer the mixture to a bowl lined with a paper towel and press out as much excess moisture as you can — this step matters, since too much liquid will keep your kebab from holding together properly on the pan.
In a large bowl, combine the ground chicken with the vegetable mixture, tomato paste, turmeric, paprika, cumin, Aleppo pepper (or crushed red pepper flakes), and kosher salt.
Mix everything together until it's fully incorporated, then transfer the meat mixture to a greased quarter sheet pan and spread it into an even, flat layer.
Using a knife, score the meat both horizontally and vertically, just like you'd see done at a restaurant. This step makes it so much easier to cut clean kebab pieces once everything is finished baking.
Transfer the pan to the oven and bake for 20 minutes, then switch the oven to broil and broil for an additional 4 to 5 minutes, until the top is golden and slightly crisp. Remove the pan from the oven and cut along the lines you scored earlier.
While the kebab bakes, make the sumac onion salad. Slice the red onion and quarter the baby tomatoes, then add both to a bowl along with the sumac, red wine vinegar, and kosher salt. Toss to combine and set aside to let the flavors meld while the kebab finishes cooking.
To assemble, spread a generous layer of garlic spread onto each pita wrap, add three slices of the kebab, and top with a scoop of the sumac onion salad. Fold and enjoy immediately while everything is warm.