In a small saucepan, whisk together soy sauce and maple syrup. Bring to a simmer over medium-high heat and cook until slightly thickened (about 3-4 minutes).

Remove from heat and whisk in Dijon mustard until smooth.

Set aside 4 tablespoons of glaze in a small bowl.

Pour remaining glaze into a large dish and add salmon fillets flesh-side down in a single layer. Refrigerate salmon to marinate for about 1 hour if time allows.

Heat 1 tablespoon of olive oil in a large skillet over medium heat. Remove salmon from marinade and shake off excess liquid (discard remaining marinade from the dish). Place salmon fillets in hot skillet and pour reserved marinade over top.

Cover with a lid and cook until salmon is browned on each side and flakes easily with a fork (about 2-3 minutes per side). Spoon pan sauce over fillets as they cook. Season salmon with salt and pepper, to taste.