Italian Sausage and Prosciutto Stromboli

Stromboli dough:
1 and 1/4 cups - water (between 110 and 115 degrees F)
1 0.25-ounce package - active dry yeast
1 tablespoon - butter, room temperature
2 tablespoons - dry powdered milk
1 teaspoon - salt
1 tablespoon - sugar
3 1/8 cups - all purpose unbleached flour
Sauce:
2 tablespoons - extra virgin olive oil
2 cloves - garlic, diced
2 14.5-ounce cans - diced tomatoes (Hunts brand preferably)
3 tablespoons - fresh basil, chopped
Salt and pepper to taste
1/2 teaspoon - red pepper flakes
Ingredients in layers:
3 tablespoons - extra virgin olive oil
2 - medium onions, chopped
1 pound - mozzarella cheese, grated
1/4 pound - prosciutto, thinly sliced
4 ounces - asiago cheese, grated
1 pound - mild Italian sausage, casings removed
Preparation:
The dough: Stir the water and yeast together in the bread maker (you can place ingredients in bowl and kneed the dough by hand if you wish) and let the yeast dissolve, about 10 minutes. Place the butter, milk, salt, sugar, and flour into the bread maker and start bread maker allowing the dough to form into a smooth ball. Remove and place on a floured surface. Cover with a damp towel and allow to rise for 30 minutes.
The sauce: While the dough is kneading in the bread maker, place the oil into a pan and heat over medium heat. Add the garlic and cook for one minute. Add the tomatoes, basil, salt, pepper, and red pepper flakes. Allow the sauce to cook (it should boil slightly) until most of the water is gone and the sauce is thick, about 30 to 45 minutes. Stir periodically.
The ingredients in layers: Add the sausage to a heavy frying pan and cook until brown, breaking the meat up into bits as it cooks. In another pan, add the oil and onions and cook until the onions are caramelized (deep brown).
The Stromboli: Preheat oven to 350 degrees F. Roll out the dough into a rectangular sheet on a lightly floured surface. Do not roll too thin.
Form layers starting with mozzarella by sprinkling it evenly over the dough. Leave a border on one of the short ends of the rectangle so you can seal the dough after it is rolled up. Place the sausage on the cheese followed by the onions.
Place the prosciutto slices on top of the onions. The sauce will be thick and hard to spread so simple drop dollops evenly spaced across the prosciutto.
Finally, sprinkle the asiago evenly over the surface.
Then roll the dough (like a jelly roll) up sealing the ends and along the seam. You should roll parallel to the longest length of the rectangle. Place the dough carefully on an oiled baking sheet (seal-side face down).
Cook in the oven for 30 to 35 minutes. Once the Stromboli has baked, cut into slices and serve.