* 3 cups fresh lemon juice
* 1/2 to 1 whole habanero chile, chopped (a whole chili will be ultra-hot)
* 1 teaspoon grated lemon zest
* 1 cup mayonnaise
* Salt and freshly ground pepper
* 1 small red onion, finely diced
* 1 large stalk celery, finely diced
* 2 tablespoons chopped fresh flat-leaf parsley
* 4 (8 ounce) tuna steaks
* Olive oil
* 8 slices hearty bread (Italian, French, ciabatta, or country white)
1. In a small saucepan, pour the 3 cups of lemon juice, and put over medium high heat; bring it to a boil and cook until liquid is reduced to 1/2 cup; remove and let cool slightly.
2. In your blender, pour the reduced lemon juice, habanero chili, lemon zest, and mayonnaise and blend until smooth; season with salt and pepper, taste and adjust as desired; then pour mixture into large bowl and add the onions, celery, and parsley; set aside.
3. Heat grill to high. Drizzle olive oil over tuna, coating lightly, then season with salt and pepper, flip and repeat.
4. When grill is hot, put tuna on grill and cook 2 minutes, flip and cook 2 more minutes, making sure you have good charred marks on both sides; you want the tuna to be browned well on the outside but rare on the inside.
5. Remove from grill and let rest for 5 minutes; then slice tuna into thin pieces.
6. Add the sliced tuna to the lemon/mayonnaise mixture and gently toss together until tuna is coated well.
7. Make sandwiches by dividing the tuna evenly between 4 slices of bread, then topping each with watercress, then covering each with remaining 4 slices.
The flavors of the spicy mayo dressing are perfect with grilled tuna. However, if fresh tuna is not available in your area, you can use canned tuna and make more of a tuna salad sandwich. Just choose good albacore tuna in water and drain it well. Then just mix in the dressing as directed.