In a medium mixing bowl, combine the shallot, vinegar, maple syrup, capers, and a pinch of salt and pepper. Allow to sit for 15 minutes, then whisk in the olive oil.
Sandwich the tuna steaks between two sheets of plastic wrap and pound until ¼-inch thick. Rub with some olive oil, and sprinkle with salt and pepper.
Preheat a griddle. Set the tuna on it, and lightly sear one side only , for about 1 minute. Transfer to plates, with the seared side up.
Fold the parsley, pomegranate seeds, and sliced fennel into the dressing, and if using, season to taste with hot sauce. Toss gently to coat, and top each tuna steak with a mound of the salad, and serve immediately.