Combine all the seasoning ingredients and mix well. Set aside 1 tablespoon for this recipe and store the remainder in an airtight container.
Use a 6-quart slow cooker sprayed with gluten-free nonstick cooking spray. Rinse the spinach leaves and place them into your slow cooker insert.
Set the salmon fillets on top of the spinach. In a small mixing bowl, combine the brown sugar and Cajun seasoning. Sprinkle this evenly over the top of the fish. Add the lime juice.
Cover and cook on high for 2 hours, or until the fish flakes easily with a fork.Serve over hot steamed rice with a lime wedge.