In a medium bowl, combine the brown sugar, garlic, ginger, and soy sauce. Add the salmon and toss until coated. Marinate for at least 30 minutes or up to overnight in an airtight container in the refrigerator.
Remove the salmon from the marinade and allow any excess to drip off. Thread the fish onto 4 skewers, dividing evenly. Heat the oil in a large skillet over medium-high heat. Once the oil is glistening, working in batches, add the salmon and sear for about 2-3 minutes per side, or until cooked through and easily flakes with a fork. Alternatively skip the skewer step and cook directly in the skillet.
Meanwhile, make the wasabi aioli. In a small bowl, whisk together the mayonnaise, wasabi paste, and lemon juice until smooth.
Serve the salmon skewers drizzled with the wasabi aioli, sprinkled with cilantro and sesame seeds (if using) alongside remaining sauce for dipping.