Preheat the oven to 425 degrees F. Line a rimmed baking sheet with parchment paper.
Place the salmon on the prepared sheet. In a bowl, whisk together the mustard, maple syrup, sesame oil and soy sauce. Pour over the salmon fillets. Bake until the salmon is opaque throughout, 8 to 10 minutes.
Serve with salad or steamed vegetables. Sprinkle with roasted black sesame seeds, if using.