Place the peppers in the oven and roast, turning frequently, until blackened on all sides (about 30 minutes total). Remove the peppers and place them immediately in a brown paper bag, folding the top over to keep (most of) the steam in. Allow them to cool.

Peel and seed the cooled peppers. Cut into strips. (The peppers may be roasted a day or two before and stored in the refrigerator, peeled and seeded, until you are ready to make the sauce.)

Place a large skillet over medium heat and spray lightly with olive oil. Add the diced onion and sliced garlic. Cook slowly for about 4 - 5 minutes until the onions begin to soften. Adjust the heat if needed: do not let the onions brown.

Add the red pepper, sage, parsley, stock, water, salt, and pepper. Cook, stirring frequently, at a simmer for about 15 to 20 minutes over medium-low heat.

While the sauce is cooking, place the water in a medium stock pot over high heat.

When the onions in the onion/peppers mixture appear soft, use a blender or immersion blender to blend until smooth.

Return the puree to the pan and add the vinegar and olive oil. Reduce the heat to very low.

Add the fettuccine to the boiling water and cook until tender.

Using tongs, transfer the cooked pasta to the sauce. Don't worry too much about transferring water with the pasta. If needed, add about 1/4 cup of the pasta water (or more) to thin the sauce a little.

Increase the heat to medium and add the arugula to the pasta and sauce.

Cook for one minute, stirring gently, and add the mozzarella.

Toss gently for about 30 seconds and serve, topped with the grated parmesan.