In a large skillet over medium high heat, add the sausage and break up while cooking, about 3-5 minutes. Remove to a plate.
1/2 Pound Hot or Mild Italian Sausage
Turn the heat to medium, add the olive oil and add the onions and peppers for about 3-5 minutes.
2-3 Tablespoons Olive Oil, 1/2 Yellow Onion, 1 Red Bell Pepper, 1 Yellow Bell Pepper, 1 Green Bell Pepper
Turn down to medium low and cook for 15-30 minutes, stirring occasionally until tender and golden in color. Add the tomatoes and cook another 5 minutes or until soft. Remove to the sausage plate.
1 Cup Grape Tomatoes
Turn the heat up to medium and add the pepperoni, cooking just until crisped. Remove all but a handful of the pepperoni to the sausage plate and drain any excess grease. Place the handful of pepperoni on a small plate for garnish.
1 Cup Pepperoni
Place all ingredients back in the skillet, including the shredded cheese, parmesan and sauce. Stir to combine and heat until warmed through. If your skillet is oven safe go ahead and proceed, otherwise transfer to a casserole dish.