In a mixing bowl, combine the soy sauce (or Tamari), mirin, and sugar. Whisk until the sugar is fully dissolved.
Place the salmon fillet in a shallow dish and pour the marinade over it, ensuring it is well-coated. Let it marinate for at least 15 minutes.
In a skillet over medium heat, add 1 tablespoon of oil. Allow the oil to heat until it shimmers.
Carefully place the marinated salmon fillet into the skillet, skin-side down. Cook for about 4-5 minutes.
Drizzle some of the leftover marinade over the salmon while it cooks on the other side. Flip and cook for another 3-4 minutes until cooked through.
Transfer the salmon to a serving plate. Sprinkle with white and black sesame seeds. Serve with rice and steamed vegetables.
