Start by preheating your oven to 375°F (190°C). While the oven heats up, make the sauce. In a medium bowl, mix the grainy mustard, Dijon mustard, honey, minced garlic, lemon juice, and olive oil.
Fold the sides of the foil over the salmon to make a sealed packet. Bake the salmon in the oven for about 15 to 20 minutes. If your salmon is thicker, it might take a bit longer. The inside temperature should be 145°F (63°C) if you use a thermometer.
To Cook On The Grill: Just move the foil packet with the salmon onto the grill. Grill for about 15-20 minutes, or until the salmon is almost completely cooked. Open the foil and grill for another 3-4 minutes.