Heat oil in a small skillet or saucepan. Add shallots and cook until tender, about 2 minutes. Add red wine vinegar, then mustard and honey. Stir until combined and remove from heat.
Spread a large sheet of heavy-duty aluminum foil on counter. If your salmon fillet is large, you may need to overlap two sheets. Line with a smaller sheet of parchment paper. Lay salmon fillet on top and brush with glaze, reserving ⅓ of the glaze to use after baking or grilling.
Fold foil over and secure the ends to enclose the salmon completely. Place on pre-heated grill and cook for 10 - 15 minutes (or bake in a pre-heated 400°F. oven) until fish flakes easily with a fork. Open foil package, brush with remaining glaze and place under the broiler for no more than 2 minutes to make the glaze a little crispy. Transfer to a serving platter and serve.
It's easy to overcook salmon. Check it at 10 minutes. If it is beginning to flake when poked with a fork but is still slightly translucent in the center of the fillet, it is probably done.Remember to let it rest for 5 minutes after removing it from the oven. It will continue to cook a little on the counter. You can check the internal temperature with an instant-read thermometer. It should be 145°F.