Boil the buckwheat noodles, rinse in cold water, and drain well.
Slice cucumber, carrot, avocado, and red onion thinly.
Cut raw salmon or chicken breast into bite-sized pieces.
Place the cooked buckwheat noodles in a bowl and top with the prepared ingredients.
Mix soy sauce, lemon juice, and sesame oil to make the sauce and drizzle it on top.