These big fish contain some mercury, but loving them is hard to resist. Serve this dish on its own for a light meal, or pair it with roasted potatoes to fill your heartier appetite.
For the tapenade
— 1 Tbs. chopped fresh flat-leaf parsley
— 1 anchovy fillet, rinsed and dried
— 1-1/2 teaspoon. capers, rinsed and drained
— 1 small clove garlic, finely chopped
— 1/2 tsp. finely grated lemon zest
— 2 Tbs. Extra virgin olive oil
For the fish and ragu
— 2 oz. (4 Tbs.) unsalted butter
— 12 cherry tomatoes, quartered
— 1/4 cup raisins
— 2 Tbs. fresh lemon juice
— 2 Tbs. toasted pine nuts
— 5 oz. (5 packed cups) baby spinach
— 1 Tbs. finely grated Parmigiano Reggiano
— 1 Tbs. extra-virgin olive oil
Making the tapenade
First of, put all the following ingredients into the food processot; olives, anchovy, garlic, capers, garlic, parsley and lemon zest until they are really finely choped. With the motor running, slowly add the oil and process until combined. Allow 1/4 cup for the fish; refrigerate the balance in an airtight container for another use.
Cook the ragu and the fish
Melt the butter in a 12-inch nonstick skillet over moderate heat. Cook, swirling occasionally, until fragrant and the milk solids are golden brown, about 2 minutes. Add the spinach and stir until just wilted, about 2 minutes, then stir in the Parmigiano, 1/2 tsp. salt, and 1/4 tsp. pepper. Transport to a bowl and cover with foil to keep warm. Wipe out the skillet.
Heat the olive oil in the skillet over medium-high heat until shimmering hot. Add the tuna and cook, undisturbed, until the bottom 1/8 inch is whitened for medium rare (1/4 inch for medium), about 1 minute. Serve with the ragu.