Allow salmon fillets to rest at room temperature for 20 minutes to promote even cooking.
Combine smoked paprika, garlic powder, onion powder, salt, oregano, thyme, black pepper, and cayenne in a bowl. Mix thoroughly.
Prepare dilly ranch or creamy herby hemp dressing, or use a high-quality store-bought ranch.
Pat salmon fillets dry and lightly brush with olive oil. Generously coat each piece with approximately 2 teaspoons Cajun seasoning, gently pressing spices into the surface.
Heat a cast iron or carbon steel pan over medium-high. Add high heat oil, then place the seasoned salmon fillets skinless side down. Sear undisturbed for 4 minutes, flip, and continue cooking an additional 3–6 minutes until just cooked through.
In a mixing bowl, toss lettuce, spinach, and sprouts with a small amount of dressing.
Lightly toast the buns in a dry pan or toaster until golden.
Layer each bun with a blackened salmon fillet, cucumber slices, red onion, and dressed greens. Drizzle with additional dressing as desired. Serve immediately.
Notes
For best results, use high-quality fresh salmon fillets.
Adjust the level of cayenne pepper to control spice levels.
Experiment with different types of buns for flavor variations.