Bring a large pan of generously salted water to boil and cook the pasta according to packet instructions.
Heat a large pan over medium heat. Add the chopped onion and cook until softened, stirring occasionally, for about 5 minutes.
Add the garlic and cook for an additional 30 seconds.
Pour in the tomato passata, tomato puree and stock.
Add the anchovy paste (or salt), black pepper, balsamic vinegar, dried oregano, and sugar. Simmer for 5-10 minutes, stirring occasionally.
It's likely the pasta will be done at this point. Make sure you reserve a little of the pasta water before draining it.
Remove the sauce from the heat and stir in the mascarpone, chopped fresh basil and lemon juice.
Toss in the pasta, add 1-2 tablespoons of the reserved pasta water if needed, and serve immediately with freshly grated Parmesan cheese and black pepper.