Use any fresh tuna with this recipe, or you could use yellowtail, amberjack, Spanish mackerel or king mackerel. If you are inland, sturgeon, paddlefish or even catfish. Really any firm fish you can cut into squares will work. Serve this roasted fingerling potatoes and a green salad, or with a Spanish style rice.
Slice the bonito or tuna into chunks about 2 inches across. Be sure cut out the "blood line," the extremely dark band of meat running along the midline of each fillet; it is very, very strong-tasting. Toss the tuna chunks in a large bowl with some salt to coat and set aside.
Make the sauce by putting everything but the olive oil in a food processor or blender and buzzing it to combine. With the motor running, drizzle in all but about 3 tablespoons of olive oil.
Get a large saute pan hot and add the remaining olive oil. Heat this for a minute or so, but don't let it smoke. Pat the tuna chunks dry with paper towels and sear them hard and fast over high heat in the pan. You will want at least two of the four sides of each chunk to get a good sear. Take your time and do not crowd the pan -- place each chunk down by hand, otherwise they will all stick in a clump if you dump them in at once. You will know when to turn the fish when you can lift up most of each chunk with tongs. Try not to scrape the bottom of the saute pan with a spatula, as this defeats the purpose of getting a good sear on the fish. It could take a good 3 to 5 minutes to get this sear, depending on how big the chunks are and how hot the pan is.
When the fish has been nicely seared off, pour in the sauce and toss to coat the fish. Turn the heat down to medium and let this simmer for 5 minutes. Add salt and black pepper to taste and serve hot or at room temperature, with fingerling potatoes, rice or crusty bread.