Cook the pasta al dente (it should have a bite to it).
Dice the onion, chop the garlic very finely.
Heat the olive oil and clarified butter in a large pan.
Add the onion and Italian seasoning, cook for about 6 minutes over medium-low heat until translucent. Add the garlic and cook, stirring, for one more minute.
Drain the tuna using a sieve, cut the olives in half or into 3 parts.
Add canned tomatoes, broth, tuna and olives to the pan. Cook, stirring from time to time, over medium heat for about 10 minutes.
Season with salt and pepper to taste, optionally with a bit of lemon juice.
Mix with cooked pasta, serve with grated Parmesan cheese and chopped parsley (optional).