Preheat your oven to 400°F (200°C) and position the rack in the top third of the oven.

Line a baking sheet with aluminum foil and lightly spray it with cooking spray.

Gently pat the Arctic char pieces dry with paper towels and arrange them skin-side down on the prepared baking sheet.

In a small bowl, whisk together the Dijon mustard, brown sugar, lemon juice, garlic powder, salt, and pepper until smooth.

Generously spread the glaze over each piece of Arctic char.

Bake the Arctic char uncovered for 10-15 minutes, checking for doneness at the 10-minute mark.

Once baked, remove from the oven and garnish with freshly chopped parsley if desired.