Season your yellowtail with salt and pepper and grill over high heat. Cook until you have created a nice crust on the outside but the interior is rare to medium rare, just barely warm.

Toast the brioche buns.

In a bowl, season your tomatoes and lettuce with olive oil, salt and pepper, and red wine vinegar.

Rehydrate the wasabi powder.

To a blender, add wasabi, Dijon, garlic, shallot, egg yolk, lemon juice, and water. Blend until smooth.

While blending, add oil until you reach the desired consistency.

Taste and season with salt.

To assemble, spread your wasabi aioli on both toasted buns. Add yellowtail, lettuce, and tomato.

In a bowl or blender mix olive oil, lemon juice, Dijon, and salt and pepper. Marinate watermelon for a few minutes in the vinaigrette. Toss in watercress and enjoy with your burger.