How to Make It
In a food processor or blender, pulse the olives, parsley, and garlic to a coarse puree with the anchovy paste, 6 tablespoons of the olive oil, the lemon juice, and 1/4 teaspoon each of the salt and pepper. Put three-quarters of the mixture in a large bowl.
Heat a grill pan or heavy frying pan over moderate heat. Coat the tuna with the remaining 1 tablespoon oil and season with the remaining 1/4 teaspoon salt and 1/4 teaspoon pepper. Cook about 1 1/2 minutes per side. Remove the tuna. Let sit for 3 minutes. The fish will be rare. Cut it into 1/4-inch slices.
In a large pot of boiling, salted water, cook the linguine until just done, about 12 minutes. Reserve about 1/2 cup of the pasta water. Drain the linguine, add it and 1/4 cup of the reserved pasta water to the bowl with the olive mixture, and toss. If the sauce seems too thick, add more of the reserved pasta water. Mound the pasta on plates and top with the tuna. Spoon the remaining olive mixture on top.