Preheat the oven broiler to high and position the rack about 6 inches below the broiler.
Line a baking sheet or leave unlined and place the 2 lb salmon fillet skin-side down; brush the top with 2 tablespoons grapeseed oil.
In a small bowl, combine 1 tsp smoked paprika, 1 tsp dried Italian seasoning, 1/2 tsp salt, 1/2 tsp black pepper, 1/2 tsp garlic powder, 1/2 tsp onion powder, 1/2 tsp crushed red pepper flakes, and a pinch of cayenne; mix well.
Sprinkle the spice mixture evenly over the top of the salmon and gently press to adhere.
Broil the salmon for 6 to 8 minutes, or until it is just opaque and flakes easily with a fork (timing will vary with thickness).
While the salmon cooks, stir together 4 tablespoons room-temperature unsalted butter, the zest of 1/2 lime, and 1/8 teaspoon coarse sea salt until smooth to make the salted lime butter.
Remove the salmon from the oven and top with a few teaspoons of the salted lime butter; serve immediately with lime wedges if desired.