Pat salmon dry and season liberally on both sides with salt and freshly cracked pepper.
Preheat cast-iron skillet over medium-high heat. Add olive oil and allow oil to heat fully.
Place salmon filets, skin side up, in hot oil. Allow to cook for about 3 min or flesh is crispy and a deep golden brown.
In the meantime, whisk together garlic, dijon mustard, maple syrup, water, and red pepper flakes.
Flip salmon and sauce to pan. Add butter, and baste salmon with a spoon another 3-4 minutes or until salmon flakes easily with a fork. Serve warm with sauce spooned over salmon.
Notes
Check for doneness: Use an instant-read thermometer to check the temperature of the salmon - it's done when it reads 125 degrees F.Alternative pan options: If you don't have a cast-iron skillet, you can use a stainless steel pan (be sure to heat the pan fully before adding oil) or a nonstick frying pan. The browning results with cast-iron will be better, but the salmon will still be delicious in whatever pan you use!Pat your salmon dry: This is an important step to get that crispy seared crust on your salmon. make sure your salmon is fully dry before seasoning it so that the oil in the pan can brown it up nicely.Atlantic (farm-raised) vs. Alaskan (wild-caught) salmon: I made this recipe using Atlantic salmon, which has a higher fat content than wild-caught salmon. If you make it with Alaskan salmon, you'll need to adjust the cook time and watch carefully that the salmon doesn't dry out.