Tuna is a staple in the Mediterranean diet, and, just as with other meats, little is wasted. Meatballs made from scraps of tuna appear in several cultures, but the Sicilians seem to eat them the most. This recipe is an amalgam of about a dozen I've read, and it works well either as a stand-alone dish or, American-style, with tomato sauce and spaghetti. If you can't get fresh tuna (you cannot use canned tuna here), use amberjack, mackerel, bluefish, king mackerel, wahoo or any dark, meaty fish.
1/3cupshelled pistachios or almonds,chopped
1/2cupchopped fresh mint
Zest of a lemon
Flour for dusting
Olive oil for frying
Chop the tuna into 1/2 inch pieces. Put the tuna, mint, pistachios and the chopped onion in a food processor and pulse to combine. You want a rough mixture, not a smooth paste. Put the tuna mixture into a large bowl with the breadcrumbs, salt, lemon zest and egg and mix well with your clean hands for a minute or so. You want everything combined well and you want the proteins in the egg and tuna to bind the mixture.
Using an ice cream scoop or large spoon to scoop out the meat, roll into meatballs. You should be able to make about 20 golf ball-sized meatballs. Roll each meatball in flour and fry in enough olive oil to come half way up the sides of a large frying pan. You will probably need about 1/2 cup. Fry gently until browned over medium heat, about 15 to 20 minutes, and set each finished meatball on paper towels to drain.
To finish, stew the meatballs in the tomato sauce (you can use any tomato sauce you want, if you'd rather not make the tomato-fennel sauce) until heated through, about 5 to 10 minutes, and serve alone or with pasta.
The meatballs can be made a day ahead, and, once cooked, will store in the fridge for a couple days or in the freezer for a couple months.