Preheat your oven to 350°F (175°C).

In a large mixing bowl, combine the ground beef, minced garlic, dried oregano, ground cumin, salt, and black pepper. Mix thoroughly until the meat becomes slightly tacky.

Press the meat mixture firmly into an 8x4-inch loaf pan, ensuring there are no air pockets.

Bake for 45 to 50 minutes, or until the internal temperature reaches 160°F (71°C).

Remove the meatloaf from the oven, carefully drain any excess fat, and let it rest on a cutting board for 10 to 15 minutes.

Slice the rested beef loaf as thinly as possible.

Heat a large skillet over medium-high heat. Add the beef slices and pan-fry for 1 to 2 minutes per side until the edges are crispy and browned.

Warm the pita breads in the microwave for 10 seconds or in a dry skillet over medium heat.

Assemble the gyros by spreading a generous spoonful of tzatziki sauce on the center of each pita.

Layer the crispy beef slices, shredded lettuce, sliced tomatoes, red onion, and crumbled feta cheese on top of the sauce.

Fold the sides of the pita bread inward to wrap the filling, and serve immediately.