Cilantro adds a nice note of freshness. If you don't like cilantro, you can use dill or parsley instead. This is super easy, but you can even prep the salmon ahead, coating it with the mix, and just pop it in the oven when ready to eat.
Preheat the oven to 400 degrees F. Line a rimmed baking sheet with aluminum foil.
Mix together the mustard, 1 tablespoon of the cilantro, the mayonnaise and maple syrup in a bowl. Put the salmon fillets on the baking sheet and sprinkle with 1/4 teaspoon each salt and pepper. Spread some of the mustard mixture evenly over each fillet.
Bake until just cooked through, 10 to 12 minute. Sprinkle with the remaining 1 tablespoon cilantro and serve.