Preheat the oven to 350°F (175°C). Lightly spray or oil a baking dish large enough for the salmon.
Pat the salmon dry and place it skin-side down in the prepared baking dish.
Brush the top of the salmon lightly with the avocado oil, then evenly sprinkle with paprika, garlic powder, dried parsley, and sea salt.
In a small bowl, stir the stone-ground mustard. If making the maple mustard variation, mix in the maple syrup.
Spread the mustard mixture over the top of the salmon so the flesh is evenly coated.
Bake on the center rack for 15–20 minutes, until the salmon is nearly cooked through.
Switch the oven to high broil and broil for about 5 minutes, or until the top is lightly crispy and the salmon reaches 145°F (63°C) at the thickest part when checked with a digital thermometer.
Remove from the oven and let rest briefly, then serve with lemon wedges and desired sides.