Preheat the oven to 375 degrees.

Start by removing the center of the onion. Cut the top off (leave the root end) and then cut around the edges, leaving two or three layers intact.

Using a large spoon, scoop out the inside as close to the bottom and edges as possible, again, leaving two or three layers.

Place them in a deep casserole dish. Add the water and bake for about 15 to 20 minutes to slightly soften. Remove from the oven and allow to cool. 

Meanwhile, brown the sausage.

When it's almost cooked, add the garlic and red pepper to the pan. Cook gently for about 5 minutes.

Add the pasta and mix well. Add salt and pepper to taste.

Scoop the mixture into the onions.

Top each with the bread crumbs and them the parmesan.

Bake for about 30 minutes.

Reduce the oven to 350 degrees. Top each onion with a slice of mozzarella and bake for another 15 or 20 minutes, or until the cheese is melted and starting to brown.

Remove from the oven and allow to cool for about five minutes, then serve.