Creamy Spinach-Stuffed Portobellos

Heat the oil in a 10-inch nonstick skillet over medium heat.  Add the onion and cook until tender-crisp, stirring occasionally.  Add the tomatoes and spinach and cook just until the spinach is wilted.  Stir in the soup and cook until the mixture is hot and bubbling.Stir the bread crumbs and cheese in a small bowl.Place the mushroom caps onto a baking sheet.  Spoon the spinach mixture into the mushroom caps.Roast at 425ºF. for 15 minutes or until the mushroom caps are tender.  Remove the baking sheet from the oven.  Sprinkle with the bread crumb mixture.Heat the broiler.  Broil the mushroom caps 4 inches from the heat until the bread crumb mixture is golden brown.