Prepare the gyro meat: In a food processor, finely chop the onion and garlic. Combine with the ground meat, salt, pepper, breadcrumbs, oregano, cumin, and Aleppo pepper in a bowl. Use clean hands or gloves to thoroughly mix the meat until it forms a dense mixture.

Bake: Pack the meat mixture into a 9x5 inch loaf pan. Bake at 325°F for about 50-60 minutes, or until the center reaches 165°F on a thermometer. Let it rest for 20 minutes, then refrigerate for a few hours or overnight, if possible, to aid slicing.

Slice the meat: Take the meat out of the pan, reserving the fat drippings, and slice it into thin strips, about 1/8 inch thick.

Brown the meat: Heat a griddle, cast iron skillet, or regular skillet over medium-high heat. Add some reserved meat drippings or a bit of oil to coat the pan lightly. Once hot, place the meat slices flat in the pan and cook for 1-2 minutes on each side until browned and crisp. Alternatively, broil on a lined baking sheet in the oven for a few minutes.

Assemble the gyros: Serve the gyro meat in warmed pita bread, topped with tomato, onion, lettuce, tzatziki, and feta.