In a food processor, pulse the pecans until they are finely chopped and crumbly. Pour them onto a plate and add the cinnamon, paprika, and salt. Mix the spices into the pecans with a fork.
Spread the mustard evenly over the flesh of the salmon. This will give you a nice "sticky" layer to bind with the pecans. Coat the top of the salmon with the crust by placing the filet skin side up in the pecan crumbs. Make sure to crust all sides of the fish (except the skin) to get the full flavor of the crust.
Place the filet, skin side down on a parchment-lined baking sheet. Bake it in the center of the warm oven for 15 - 20 minutes depending on the thickness, until the fish flakes easily.
Serve immediately with a side of your favorite veggies – we went with roasted potatoes and a simple salad.
Store in an airtight container in the fridge for up to 3 days, or in the freezer for up to 3 months. Reheat in a baking dish covered in aluminum foil for 12-15 minutes at 275F.