Tuna Crudo appetizers are delicate slices of raw tuna, drizzled with a light lemon vinaigrette and served with cucumber slices in Belgian endive boats.
Combine the olive oil, lemon juice, caper brine, and red pepper in a small bowl. Set aside.
Slice the cucumber into thin slices and add to a bowl of ice water. With a sharp knife, slice the brown cut end from each endive and carefully remove a layer of leaves. Slice off the end again to release the next layer of leaves. Continue the process until you have about 20 leaves approximately the same size. Reserve any unused portions of the Belgian endive for another purpose.
Remove the partially thawed tuna from the refrigerator and place on a clean work surface. Using a very sharp, thin-blade knife, cut the tuna into 1/4-inch slices. Add the sliced tuna to a plate and drizzle the vinaigrette over it. Allow to marinate for 5-minutes while preparing the serving plate.
Remove the cucumber slices from the cold water and place on an absorbent kitchen towel, blot dry with paper towels.
Arrange the Belgian endive ‘boats’ on a serving platter, add a slice of cucumber and then two slices of the tuna to each boat with a tiny drizzle of vinaigrette. Garnish with capers and fresh herbs.
Notes
Partially freeze the tuna: If the tuna loin hasn’t been frozen, pop it in the freezer for 15 minutes. It’ll firm up just enough to make slicing easier.Choose your olive oil wisely: Extra virgin olive oil flavor varies based on the olives. Ripe olives produce a milder, more aromatic oil, while green olives give a punchier, slightly bitter flavor. Use one you know tastes good.About the cucumber: We prefer English cucumbers (the long ones wrapped in plastic) because they’re mild and nearly seedless. A mandoline makes slicing a breeze, and a quick soak in cold water makes the slices extra crisp.Don’t waste the endive: Leftover Belgian endive is great in salads, roasted with olive oil and salt, or sautéed as a simple side dish.Storage: Store any leftover tuna crudo in an airtight container in the fridge and eat within one day.