Chop your onion into large chunks, place the onion into a food processor and pulse until it is finely minced.
Remove the minced onion from the food processor and place it onto a couple paper towels. Wrap the onions up and squeeze the excess juice from the onions.
Place minced onions into a bowl with your ground lamb and beef. Add to the bowl your minced garlic and gyro seasoning. Mix everything together and place it all into the food processor.
Pulse the food processor for about 1-2 minutes, until your meat mixture is well blended and has a tacky, paste-like feel.
Scoop the meat out of the processor and into a loaf pan, you don’t need to grease your pan. Press the meat mixture into the pan evenly.
Cover the gyro meat in foil and bake for 40 minutes. Remove the foil and bake for an additional 20-25 minutes, the internal temperature needs to reach 165 degrees fahrenheit.
When the meat is fully baked, pour off any excess fat from the pan, remove the meat from the pan and allow the loaf to cool for at least 20 minutes.
Slice and serve! Traditionally gyro meat is served on a pita with fresh sliced onion, tomato, lettuce, and tzatziki sauce.