Remove the top and skins of the onion. Core out the center of the onion with an apple corer, leaving a small portion at the bottom so as to not cut completely through. Insert one bouillon cube and one large peeled garlic clove into the center of the onion.
Slice through the center towards the outer edges about an inch without slicing through. Insert slices of butter between cuts saving some for the center to place on the top of the bouillon cube.
Sprinkle with onion powder.
Wrap the onion tightly in heavy duty silver foil and place on the gas grill or directly on the coals of your charcoal briquets. Leave to cook about 60 minutes or until onion is tender and well cooked.
Sprinkle with parmesan cheese and serve with crusty french bread or bruschetta.
Prepare one onion for each serving required.