Preheat your oven to 400° F.
Peel and core the onions. Take a thin slice off the bottom if necessary to make them sit upright and level. Starting in the center, make slices in the onion to the outer edges but not slicing all the way through the onion. Place the onions in a baking dish.
Fill each onion with 1/4 tsp pepper, 1 tsp beef bouillon, 1/2 tsp soy sauce, 1/2 tsp Worcestershire sauce and 1 Tbsp of butter.
Cover with foil, bake at 400° for about 30 minutes. All ovens are different, check the onions at the 15 minute mark to see how they're doing.
When the onions are cooked through, place 1 Tbsp of grated Parmesan cheese on top of each onion, turn the oven off, and place the pan back into the oven until cheese has melted.