Tuna in oil: ， onion: ， Parmesan cheese: ， lemon: ， Rigatoni: ， rosemary: ， tomato: ， butter: ， extra v olive oil: ， pepper: ， salt:
1finely slice the onion, simmer the onion slices in melt butter for 5 mins in the pan
2meanwhile, heat the water to boil, season with salt, cook the rigatoni according to the package instruction
3dice the tomato and pick off the rosemary, stir fry with the onions in the pan, simmer with lid on
4drain the oil from the tuna, add them into the the pan
5drain the Rigatoni when done, put into the pan, toss together
6shred Parmesan cheese over the pan, toss again
7season with salt and pepper, and lemon juice
8put on a plate, decorate with rosemary, more cheese shred and a good splash of extra virgin olive oil
Be sure not to get cheap canned tuna like I did here. Not only bad for presentation, also bad for taste...