Step 1: Begin by preparing your onion. Peel and roughly chop your medium yellow onion. Place it into a food processor and pulse until it's very finely minced, almost a paste. This fine texture is crucial for integrating seamlessly into the gyro meat mixture.
Step 2: In a large mixing bowl, combine the finely minced onion with the ground lamb and ground beef. Add the minced garlic, dried oregano, dried marjoram, dried thyme, ground cumin, garlic powder, onion powder, salt, and black pepper.
Step 3: The key to authentic gyro meat texture is thorough mixing. Use your hands to really work the spices and onion into the meat. Knead the mixture vigorously for about 5-7 minutes. This process helps to break down the meat proteins, creating a sticky paste that will bind together beautifully. For an even finer, more uniform texture, you can transfer portions of the meat mixture back into the food processor and pulse a few times until it forms a smooth, pasty consistency.
Step 4: Preheat your oven to 325°F (160°C). Lightly grease a standard 9x5 inch loaf pan.
Step 5: Firmly press the meat mixture into the prepared loaf pan. It's incredibly important to pack it down as tightly as possible, eliminating any air pockets. Use the back of a spoon or your hands to really compact the gyro meat.
Step 6: Place the loaf pan on a baking sheet (to catch any drips) and bake in the preheated oven for 60-75 minutes, or until the internal temperature reaches 165°F (74°C) when measured with a meat thermometer. The loaf should be firm and browned on top.
Step 7: Once baked, carefully remove the loaf pan from the oven. Drain any accumulated fat. Place a clean, heavy brick or another heavy, oven-safe object wrapped in foil on top of the cooked gyro meat loaf. Let it rest for at least 15-20 minutes with the weight on top.
Step 8: Once cooled (and ideally chilled for a few hours or overnight for easier slicing), carefully invert the loaf pan to release the gyro meat. Transfer it to a cutting board.
Step 9: Using a very sharp knife, a meat slicer, or even a mandoline (with caution!), slice the gyro meat as thinly as possible. Aim for shavings rather than thick slices.
Step 10: To achieve that delicious crispy edge, heat a large skillet or cast-iron pan over medium-high heat with a tablespoon of olive oil. Add the thinly sliced gyro meat in a single layer, being careful not to overcrowd the pan. Cook for 2-3 minutes per side, until lightly browned and slightly crispy. Work in batches if necessary.
Step 11: Serve your crispy gyro meat immediately in warm pita bread with homemade tzatziki sauce, fresh tomato slices, thinly sliced red onion, and a sprinkle of chopped parsley or dill.