To crust the tuna steaks, pour out some of the pepper mix onto a plate, and press the tuna steaks into the pepper on both sides. Set aside.

To make the sauce, add the cream, wasabi paste, soy sauce, and xanthan gum to a small saucepan. Whisk the ingredients together, then cook on a low heat until it has warmed through and thickened.

Heat a hot skillet and fry the steaks until cooked to your liking.

Transfer the tuna to a cutting board and cut them into slices. Place the tuna on a serving plate, then pour the wasabi sauce over the top. Garnish with a few slices of green onion.