Heat your oven to 400 degrees.
Combine Dijon mustard and brown sugar. Adjust to the desired amount of sweetness-tanginess. Salt and pepper the fish.
Line a cooking sheet with foil. Lightly oil the sheet; then add fish skin-side down. Spread the tops of the fillets with the mustard mixture. Place on the highest rack in oven.
Roast for about 12 minutes.
Adapted from the NYTIMES Cooking site: https://cooking.nytimes.com/recipes/1017244-roasted-salmon-glazed-with-brown-sugar-and-mustard