Wash and dry steelhead. Layer two sheets of foil together, large enough for the steelhead fillet, and fold up the sides. Place fillet on foil.

To make the pesto, in a food processor, combine basil, olive oil, garlic, salt, pepper, honey, and lemon. Process until smooth. Add in finely ground cashews and continue to blend until smooth.

Spread pesto evenly on fish. Slice tomatoes and place on top.

Barbecue or bake in oven. Cooking time will depend on thickness of fillet. Use the back of a spatula method to see if fish is done. (Press on the fish using the back of a spatula. If fish is firm, then it is done. If it is spongy, you need to keep cooking it.)