Variations (if you want)
You can add some yummy sautéed mushrooms, any kind you like. I like the earthy ones, crimini, shitake or chanterelles are good. Just cook these with the onions and garlic at the beginning.
I also love to dollop some Mascarpone or Ricotta INTO THE BOTTOM of the plate. When you place the hot Cappellini and sauce up top it melts it down and creates a delicious, rich creaminess.
For presentation, a little drizzle of olive oil on top of the plated pasta adds flavor and a beautiful glistening sheen.