1. In a large Dutch oven over high heat, sear all sides of the beef in the olive oil until completely browned (at least four or five minutes per side).
2. Remove beef to a platter.
3. Reduce heat to medium high and add 1 pound of the onions and cook for three minutes stirring occasionally.
4. Add wine (or beef stock) to deglaze and cook down for two minutes. Remove from heat.
5. In the bowl of a slow cooker, place 6 tomato halves along bottom. Place seared beef over tomatoes and top with liquid from the Dutch oven. Add pepper, Italian herbs, sugar, celery salt, garlic powder, onion powder and bay leaves. Cover and cook on high for 8-10 hours. Ours was fall apart tender in 9 hours.
6. Once the beef is tender, remove to a cutting board and either slice against the grain or shred like pulled pork with two forks. Add a few of the cooked tomatoes and onions to form a moist beef filling.
7. Take the remaining fresh tomato and fresh onion and dice small and add to the sliced pepperoncini.
8. To serve, line each sub roll with two slices of provolone, divide the hot meat between the six rolls and top with the tomato, and onion mixture.
9. The hot cooking liquid can be used to dip the sandwich (similar to a French dipped sandwich) but this step is optional.