Pasta Salad with Seared Tuna and Citrus Dressing

• FAST
• MAKE-AHEAD

Ingredients

1. 1/2 pound spaghettini
2. 2 tablespoons red-wine vinegar
3. 1/2 teaspoon grated orange zest (from about 1/4 orange)
4. 1 tablespoon fresh orange juice
5. 1 tablespoon lemon juice
6. 1 teaspoon Dijon mustard
7. Salt
8. Fresh-ground black pepper
9. 6 1/2 tablespoons olive oil
10. 2 cucumbers, peeled, halved lengthwise, seeded, and cut crosswise into thin slices
11. 6 tablespoons chopped fresh mint
12. 1 pound tuna steak, about 1 inch thick

1. In a large pot of boiling, salted water, cook the spaghettini until just done, about 9 minutes. Drain. Rinse with cold water; drain thoroughly.
2. In a large glass or stainless-steel bowl, whisk together the vinegar, orange zest, orange juice, lemon juice, mustard, 3/4 teaspoon salt, and 1/4 teaspoon pepper. Add 6 tablespoons of the oil slowly, whisking. Add the spaghettini, cucumbers, and mint and toss.
3. Heat a grill pan or heavy frying pan over moderately high heat. Coat the tuna with the remaining 1/2 tablespoon oil and sprinkle with 1/8 teaspoon salt and a pinch of pepper. Cook, turning once, until done to your taste, about 2 minutes per side for medium rare. Remove. Cut the tuna into 1-inch chunks and toss with the spaghettini.