Cook fettuccine as per packet.
In a large frypan over medium heat, bring the cream and sweet potato to a gentle simmer for 5 mins, until thickened slightly.
Add the tomato paste, olive oil, lemon, salt and parmesan and stir through until well combined. Leave on heat until reaches a gentle simmer.
Remove from heat and add the fettuccine to the sauce and toss well to coat.
Serve topped with extra parmesan.
If adding chicken or salmon, cook meat separately and stir through at the end with the pasta.