Baked Lamb Gyros

¼ cup chopped onion
½ pound ground lamb
½ pound ground beef
1 teaspoon minced garlic
½ teaspoon dried oregano
½ teaspoon ground cumin
½ teaspoon dried marjoram
½ teaspoon sea salt
¼ teaspoon dried thyme
¼ teaspoon dried rosemary
¼ teaspoon ground black pepper

Place onion in a food processor; pulse until very finely minced. Transfer to paper towels and squeeze out excess liquid.
Transfer drained onion to a large mixing bowl; add remaining ingredients and mix thoroughly with hands. Cover and refrigerate 2 hours.
Preheat oven to 300°F. Transfer lamb mixture to a greased small meatloaf pan, pressing down and smoothing top over.
Bake until meat reaches an internal temperature of 165°F, about 45 to 60 minutes. Cool 15 minutes on wire rack; invert and remove from pan to cool completely.
Slice lamb loaf into very thin slices. Serve inside gyro pitas with lettuce, yogurt sauce, and chopped vegetables.