The bottarga in the photo is the mullet - the tuna is darker and more intense.
This traditional seasoning adds the most luxurious and intoxicating flavor to a simple bowl of pasta. The sac of roe of the tuna is harvested from the fish whole, encased in salt to draw out the moisture, pressed under slats of wood, and finally sun-dried for just under a week. But from this cake of dried fish eggs comes the most gloriously intense seasoning. Grated finely or sliced paper thin, this Sicilian delicacy is an age-old tradition whose roots go back more than 2,500 years. Many fish loving cultures have curing traditions similar to bottarga, but it is the Italian islands whose passion for this salty delicacy runs the deepest.
We understand the apprehension in buying a whole piece of bottarga if you're thinking of one special dish. May we suggest splitting it with a friend, or follow the advice of our good friend Rolando..."rub down the cake with a good quality olive oil, wrap it in plastic and then foil and store it in the refrigerator." Rubbed down once a week, it should keep for at least 3 months. For an even longer shelf-life, make friends with your local butcher or fish monger - they'll likely have a vacuum packer and they'd be happy to seal it back up for you. (Tell them we said so!)
Grate some fresh bottarga over a pan of spaghetti with good extra virgin olive oil, chili flakes and parsley - thicken the sauce with the pasta cooking water and you're good to go!