How to Make It
Stir together coriander seeds, caraway seeds, fennel seeds, paprika, 1 1/2 tablespoons salt, and 2 teaspoons pepper in a small bowl. Rub mixture all over beef; place on a wire rack set inside a large rimmed baking sheet. Let stand at room temperature 1 hour.
Preheat oven to 450°F with oven rack in top third of oven. Rub beef with 2 tablespoons olive oil. Roast until an instant-read thermometer inserted in thickest portion registers 120°F, 35 to 40 minutes. Remove beef; let rest until completely cool, about 1 hour. Wrap tightly in plastic wrap; refrigerate until chilled, 2 hours.
Whisk together vinegar, mustard, capers, parsley, remaining 1/3 cup oil, remaining 1 1/4 teaspoons salt, and remaining 1/4 teaspoon pepper in a small bowl. Untie beef; cut into 1/4-inch-thick slices. Serve chilled or at room temperature with arugula and vinaigrette.