Place the chuck roast in the freezer for about 30 minutes before prepping; this slightly freezes the meat and makes it much easier to handle. Using a sharp knife, cut the beef against the grain into ultra-thin, 1/4-inch strips.

In a large mixing bowl, whisk together the olive oil, shawarma spice blend, minced garlic, lemon juice, salt, and black pepper. Add the thinly sliced beef to the bowl and toss until every piece is coated evenly.

Heat a large heavy-bottomed skillet or cast-iron pan over medium-high heat until very hot. Add the marinated beef slices in a single layer, working in two batches if necessary so you do not overcrowd the pan.

Let the beef cook completely undisturbed for 2 to 3 minutes to develop a dark, crispy, caramelized crust on the bottom. Stir the meat and continue cooking for another 3 to 4 minutes until perfectly browned and cooked through, then transfer to a plate.

Reduce the heat to low and place the pita breads into the hot skillet, one at a time, for about 30 seconds per side. This warms them up, makes them pliable, and allows them to soak up any remaining savory beef drippings.

To assemble the wraps, spread a generous spoonful of Greek yogurt down the center of each warmed pita. Top with the hot crispy shawarma beef, shredded lettuce, diced tomatoes, and sliced red onion, then roll up tightly and enjoy immediately.