Preheat oven to 425 °. Place cast iron skillet in the oven while it preheats. This allows the skillet to get to the perfect hot temperature for pan frying.
Rinse and pat dry the 2 pieces of salmon fillet, then place on a cutting board for prepping.
In a small bowl, combine the garlic, shallot, dijon, mayonnaise and maple syrup. Mix well until combined. Spread the mixture evenly on top of both cuts of salmon.
In a medium microwave safe bowl, add the butter and place in the microwave for 20 seconds, until the butter is melted. Remove from the microwave and let cool for a few minutes.
To the butter, add in the 2 tablespoons of olive oil, panko, and fresh parsley. Stir together until combined. Layer the panko mixture on top of the dijon sauce on the salmon. Press down lightly, so that it packs together a bit.
Remove the cast iron skillet from the preheated oven, and place on the stovetop over medium high heat. Add 2 tablespoons of olive oil to the hot skillet.
Carefully place the salmon fillets in the skillet, side by side, skin side down. Cook over medium-high heat (you want to be on the higher side) for 3-4 minutes, without disturbing.
Place the entire skillet in the oven, on the middle rack. Cook for 10-12 minutes, until the thickest part of the fillet reaches an internal temperature of 125°.
Top with a few savings of lemon zest. Cut each salmon fillet in half for 4 equal servings. Serve with a lemon quarter on each plate for squeezing the juice on top.
