Mix the marinade and put the meat in with it in a bag. Take all the air out and put the bag in the refrigerator for at least 1 hour but not more than 3.
Take a boing knife and butterfly the roast. Put the spinach and caramelized onions in the center of the roast. Sprinkle some of the cracked black pepper on it.
Roll the roast up and use toothpicks to secure it.
Wrap the butcher's twine around the roast and after securing it, remove the toothpicks.
Put the remaining black pepper on your cutting board and roll the roast in the pepper.
Put the roast on the spit and secure it according to the manufacturer's directions.
Roast at 390 for 35-45 minutes for the air fryer or about 90 minutes on a regular rotisserie. Roast until an instant-read thermometer registers your preferred style, rare, medium-rare, or medium.
Let the roast rest for about 10 minutes removing it from the spit and carving it.
Notes
Please don't insult a lovely piece of meat by cooking it well done as it becomes shoe leather - unless of course, you are out of shoes!
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