Bring pot of salted water to boil and cook ravioli for 6-8 minutes.
While water is warming, heat a sauté pan on medium-high. Add enough olive oil to coat the bottom of the pan. Add pepper and cook about 4 minutes, tossing occasionally. Add garlic cloves, stir, and season to taste with salt and pepper. Reduce heat to medium and cook another 3-4 minutes or until peppers are soft and garlic is golden. Add nduja and a ladle of pasta water and stir to combine. Reduce heat to low.
Add cooked ravioli to sauté pan and gently combine. Plate and top with desired amount of fontina.