In a small bowl, combine the smoked paprika, garlic powder, onion powder, dried oregano, cayenne pepper, sea salt, and black pepper to create the blackening spice rub.
Pat the salmon fillet and shrimp dry with paper towels. Rub the spice mixture evenly over all sides of the seafood.
Heat the avocado oil in a cast-iron skillet or non-stick pan over medium-high heat until shimmering.
Place the salmon in the pan skin-side up (if applicable) and sear for 3-4 minutes until a dark crust forms. Flip and cook for another 2-3 minutes until cooked through.
Add the shrimp to the pan during the last 3 minutes of the salmon's cooking time, searing for about 1.5 minutes per side until opaque and slightly charred.
While the seafood cooks, assemble the salad by tossing the mixed greens, sliced cucumber, and halved cherry tomatoes in a large bowl.
Top the greens with the blackened salmon and shrimp. Garnish with sliced avocado and drizzle the entire salad with fresh lemon juice before serving.