Get a pot of heavily salted water boiling for your pasta and cook pasta, timing it to add straight into the sauce at the end.
Heat the olive oil and butter in a big frying pan over medium - high heat and add onions.
When sizzling, lower the heat to medium - low and cook for 4 - 5 minutes until soft.
Add the garlic and pepper and cook for a further minute or two.
Add the tomato paste and whisk to combine, cooking for a minute or two.
With the heat still low - medium add the cream and whisk to combine evenly.
Add the lemon juice and whisk in quickly.
Add the finely grated parmesan in three separate lots, whisking in between to make sure it has melted.
Add your pasta straight into the sauce with a splash of pasta water (about ¼ cup).
Taste for seasoning and add salt to taste.
Serve and enjoy.
