In a small bowl, mix together the paprika, cayenne, garlic powder, dry mustard, and oregano and set aside. Use1 tablespoon of the olive oil to grease the sheet pan. Place the salmon, skin-side down, on a flat surface and season it with salt. Drizzle the salmon with 2 tablespoons of the oil. Transfer the spice mixture to a small fine-mesh sieve or strainer and sift an even layer of spices over the salmon. arrange the fillets skin-side down on the prepared sheet pan, leaving space between them.