Fresh Tuna Pâté Scented with Rosemary

I could eat this tuna butter spread thickly on my morning toast, but most people will prefer it with a glass of white wine as an apéritif. Be very careful not to overcook the tuna as it will make a dry pâté. This is also good with green peppercorns folded in at the end.

• 6 large sprigs fresh rosemary
• 2 tsp. olive oil
• 8 oz. very fresh tuna
• 6 oz. (12 Tbs.) unsalted butter, at room temperature
• 2 Tbs. fresh lemon juice
• Kosher salt and freshly ground black pepper 
• Crostini or crackers, for serving.

Arrange the rosemary in an even layer in a nonstick skillet, add the oil, and heat over medium until the herbs are fragrant. Lay the tuna on the rosemary sprigs and cook until the cooked white of the flesh has traveled about one-third of the way up the side of the tuna steak, about 5 minutes. Turn the tuna over and cook until cooked but still quite pink inside, another 5 minutes. (The tuna will continue to cook as it cools.) Remove the tuna from the pan and allow it to cool (pull off any clinging herbs).

In a food processor, combine the cooled tuna, the butter, lemon juice, salt, and pepper and process until smooth. Put the spread into a ramekin or small bowl, lightly cover the top with plastic wrap, and refrigerate until set. Grind more pepper over the top before serving with crostini or crackers.