Make the marinade. Combine the maple syrup, lemon juice, dill, dijon mustard, grainy dijon mustard, black pepper, and salt in a medium bowl. Measure 3 tbsp of this glaze into a small bowl and set aside for basting the salmon. 

Pour marinade into a shallow baking dish. Gently place the salmon, flesh-side down, into the marinade, while making sure not to get marinade on the salmon skin. Let this rest on the counter for 30 minutes. 

Preheat the oven to 400º F. 

Prepare a baking pan by lining it with parchment paper or spraying it with cooking spray. Remove the salmon from the marinade and place on the pan, with the skin side down. Discard the used marinade. 

Bake in the preheated oven for about 10 minutes. Remove from the oven and drizzle with the remaining 3 tbsp of maple glaze. Turn the oven to broil and return the pan to the oven for about 2 more minutes or until the salmon reaches your desired doneness. 

Remove from the oven, transfer the filets to a plate, cover loosely with foil, and let them rest for 10-15 minutes. 

Season with salt and pepper. Serve with slices of lemon, garlic rice and soy sauce.