Bring a large pot of water to the boil and add salt. Heat the olive oil in a large sauté pan over medium-high heat.
Add the pasta to the boiling water and cook according to package directions, about 8 minutes. I use pasta large enough to be lifted out of the pot with a kitchen spider (strainer) without falling through the holes.
Meanwhile, add onions and pine nuts to the sauté pan and sauté for 1 minute. Add in the garlic, raisins, parsley, about 1/2 teaspoon salt and the pepper.
Turn the tuna out into the pan and break up slightly into smaller pieces to incorporate. Add the chicken broth, fennel and bell pepper. Cover and cook for 3 to 5 minutes, until fennel is tender. You want the liquid to be absorbed, but if it gets too dry, add in a little of the pasta cooking water to keep the mixture moist.
Drain pasta or remove with a spider. Transfer pasta to a large serving bowl, top with the tuna mixture and toss. Top with nice big shavings of Grana Padano and serve with a tossed salad and crusty bread.
Note: If you are new to fennel, cut off the green stalks where they meet the top of the white bulb, which s actually tightly packed leaves, like celery. Trim a thin slice off the bottom of the base and discard any tough or blemished outer leaves. Use a sharp knife or mandoline to thinly slice the fennel. Add the stalks to stocks, and use the fronds as a fresh herb.