How To Make Naomi Pomeroy's Coriander Seared Tuna

Ingredients

• 1 1/2 pounds center-cut ahi tuna
• 1 fennel bulb
• 1 large or 2 small Valencia oranges
• 1 grapefruit
• 1 tablespoon cider vinegar
• 1 teaspoon finely minced shallot
• 1 teaspoon salt
• 3/4 teaspoon freshly ground black pepper
• 2 tablespoons extra-virgin olive oil
• 1/4 teaspoon champagne vinegar
• 1 teaspoon coriander seeds
• 1/4 cup loosely packed flat-leaf parsley leaves
• 2 tablespoons canola or grape-seed oil