Place the garlic, peppers, onions, adobo sauce, vinegar, lime juice, cumin, oregano and cloves in the bowl of your food processor and blend until combined.
Season the beef with the salt and pepper. If you have a slow cooker that you can sear in, heat it to the highest setting. If not, heat a large pot or skillet over medium-high heat. Add the oil (to either, whatever you’re using) and once it’s hot, add the beef and sear until deeply golden on every side, about 2 minutes per side.
Place the sauce mixture in the bottom of the slow cooker (and if the beef was seared in there, just lift up the beef and pour it underneath) with the beef over top. Cook on low for 8 to 10 hours, or until the beef falls apart.