Add a generous amount of neutral oil, like vegetable oil or grapeseed oil, to your skillet — enough to coat the bottom of the pan. Heat over high heat until the oil starts to smoke.
Carefully place one salmon fillet into the hot pan, skin-side down. As soon as the fillet hits the pan, press down on it with a spatula until the fillet flattens out (this only takes seconds) while bringing the heat down to medium. Pressing the fillet keeps the skin firm against the pan and will give you crisp results without curling your fillet upward. Let your salmon cook for about six minutes, or until you can see a nice golden brown color on the edge of the skin. DO NOT touch, push, or try to budge your salmon beforehand, or you'll tear the skin. Once you see the golden edges, carefully slide your spatula underneath the fillet and turn it over. (If it doesn't release, give it another 30 seconds and try again.)
Once you've flipped your salmon, it's likely a little over halfway cooked so it only needs another 2-3 minutes of cooking. If you have a meat thermometer, remove the salmon once it's reached an internal temperature of 140-145 degrees F. If you don't have a meat thermometer, cook the fish until it's opaque, and then go order a meat thermometer
Once the fillet is cooked, carefully remove it from the pan and set it on a plate; cover with tin foil so it stays warm. Repeat the same process for the other fillet.
Once the fillets are done, plate, and spoon the concord grape sauce evenly over each fillet.