Get your pasta cooking in a pot of well salted boiling water according to packet instructions. I like to undercook pasta ever so slightly so I can finish it off in the sauce.
Heat the olive oil in a pan that will be able to fit all the pasta and sauce in at the end over medium heat.
Fry the sausage meat, breaking it up with a wooden spoon. You want to get a bit of colour on it, 4 - 5 minutes.
When almost cooked all the way through, add the butter and then the garlic and cook for 30 seconds.
Add the tomato paste and mix well, cook for a further 1 - 2 minutes.
Turn the heat down slightly and add the cream and bring to a really gentle simmer. The cream will look like it doesn't want to mix well because of the fat from the sausage. Give it a whisk or a vigorous stir and it will combine well.
Add the lemon juice and pepper.
Add the grated parmesan in a few lots, letting it melt in between each addition.
If your pasta isn't quite done you could at this point turn the heat off while you wait.
When pasta is almost done add ¼ cup pasta water and mix in well.
Add pasta straight into pan and let it bubble away really gently for a minute or two.
Serve between bowls and top with extra parm, black pepper and lemon zest.