Combine salt, pepper, garlic powder, parprika, onion powder, rosemary, and cayenne pepper in small bowl.
Place the beef roast on a sheet pan, cover lightly with sunflower oil, and coat on all sides with the the spice blend.
Cover with plastic wrap and refridgerate for at least 4 hours.
Make the Basting Sauce
After 4 hours, remove the beef from the refrigerator and let come to room temperature for 30 minutes.
During this time, combine in a small mixing bowl, the vinegar, sunflower oil, crushed garlic, and Dijon mustard. Mix well.
Grilling the Beef
Preheat the grill to high and lightly oil the grates.
Once heated, place the beef on the grill and brush with the basting sauce. Cook beef for 5 minutes, flip, baste, and then repeat the flipping and basting every 5 minutes, for a total of 25-30 minutes or until the internal temperature reahces 130 degrees. (use an probe thermometer to check temp)
Remove from the grill and let rest at least 10 minutes before slicing.
Serving and Storage
Cut the beef into slice and eat right away, or portion in containers and freeze up to two months.