Whisk together the spice blend ingredients in a small bowl or jar.
Pat the salmon fillets dry, then liberally sprinkle the spices on both sides.
Working in small batches, melt 1 tbs butter per filet that will fit in a large skillet over medium-high heat. Cast iron works great for this. Wait until the butter has melted and is bubbly before adding the salmon. Add the salmon to the skillet skin side up, and leave alone. Let cook until the bottom is browned, about 5-6 minutes. Flip and cook to crisp the skin, about 2-4 minutes.
If necessary, add more butter and let melt to bubbling before cooking the remaining filets.
Serve warm with your favorite sides.
We just love salmon with a side of succotash (even though it's not quite Cajun) but it's wonderful with collard greens or a light salad as well.