Process the onion in a food processor until finely chopped.

Scoop the chopped onion onto the center of a towel, gather the ends, and squeeze out all the liquid.

Return the onion to the food processor and add ground lamb, ground beef, minced garlic, ground cumin, ground oregano, ground rosemary, ground marjoram, ground thyme, ground pepper, and sea salt.

Process the mixture until it is a fine paste, approximately 1 minute, scraping down the sides of the bowl as needed.

Taste a small patty (optional).

Cover the mixture and refrigerate for 1 to 2 hours, or preferably overnight, to allow the flavors to blend.

For Oven Roasting: Preheat the oven to 325°F (163°C).

Place the meat mixture into a loaf pan, pressing firmly to avoid air pockets.

Place the loaf pan into a water bath.

Bake for 60 to 75 minutes, or until the mixture reaches an internal temperature of 165°F (74°C).

Remove from the oven and drain any fat.

Place the loaf pan on a cooling rack, place a brick wrapped in aluminum foil directly on the surface of the meat, and let it sit for 15 to 20 minutes, until the internal temperature reaches 175°F (79°C).

For Rotisserie: Form the meat mixture into a loaf shape.

Place the loaf on top of two overlapping pieces of plastic wrap, at least 18 inches long.

Roll the mixture tightly in the plastic wrap, removing any air pockets.

Twist the ends of the plastic wrap until the surface is tight.

Store in the refrigerator overnight to allow the mixture to firm up.

Preheat the grill to high.

Place the meat onto the rotisserie skewer, with the spit forks facing inward but not touching the meat.

Line a large drip tray with double foil.

Cook on high for 15 minutes.

Decrease the heat to medium and continue to cook for another 20 to 30 minutes, or until the internal temperature of the meat reaches 165°F (74°C).

Turn off the heat and allow the meat to continue to spin for another 10 to 15 minutes, or until the internal temperature reaches 175°F (79°C).