Preheat oven to 350 degrees F. Slice about 2 inches deep through the top of the bread, and continue to cut a large rectangle. Remove top of bread and hollow out 2 inches deep to create a shallow rectangular bread bowl. Set aside. Heat 1 tablespoon olive oil over medium high heat. Add onions and sauté for approximately 5 minutes or until soft. Add red bell pepper and garlic and sauté for one minute. Stir in spinach, pesto, Worcestershire sauce, paprika, salt, pepper and mayonnaise until well combined and spinach is warmed through. Reduce heat to low and stir in cream cheese until melted. Stir in sour cream, Parmesan cheese and cheddar cheese until combined. Spoon spinach dip into prepared French bread and top with 1/2 cup mozzarella cheese. Bake on a baking tray at 350 F degrees for 25-30 minutes or until cheese is melted and slightly golden. Let bread sit approximately 5 minutes to cool (just so you don't burn yourself) then slice. Best served warm