Fettuccine Romano

Directions

1. 1
   Bring a large pot of salted water to a boil. Add the pasta and cook, according to the package instructions, until just shy of al dente. Drain the pasta thoroughly, reserving 1/2 cup of the pasta cooking water for the sauce.
2. 2
   In a large skillet, heat the butter and olive oil over medium-high heat until hot. Add the garlic and cook until just fragrant (about 1 minute). Reduce the heat to medium, add the onions, and cook until very soft and beginning to caramelize, stirring occasionally, about 10 minutes.
3. 3
   Add the tomato paste, diced tomatoes, and reserved 1/2 cup of pasta cooking water. Season with salt and pepper and cook over medium-high heat until the sauce begins to thicken, about 5 minutes. If it looks too dry, add some water.
4. 4
   Stir in the sour cream.
5. 5
   Add the cooked pasta to the skillet and toss to combine. Add the grated cheese; toss well.
6. 6
   Divide the pasta equally among bowls and top with the chopped parsley, plus extra grated cheese, if you like.