You can find Tonnino tuna some specialty and health foods markets, or visit http://www.tonnino.com.
- Heat oil in a large saucepan. Add onions and cook over medium heat until soft and translucent, about 5 minutes. Add garlic, red pepper flakes, and anchovies, stir and cook for a minute or so. Add tomatoes, capers, and salt, bring to a simmer and cook for 20 minutes, stirring often. Add tuna, leaving it in large chunks, and keep warm over low heat.
- Cook linguine in a large pot of boiling water until just al dente. Drain and put in large serving bowl, toss with sauce. Pass grated cheese on the side.