Season each salmon fillet with about 1 teaspoon Cajun spice. Heat the olive oil in a large pan, and cook the salmon over high heat about 2-3 minutes per side, or until it is cooked to your liking.
For the relish:
Peel and dice the mango into small pieces (about 1/4 - 1/3 inch). Remove the seeds and the pith from the red bell pepper and dice the bell pepper into small pieces about the same size as the mango.
In a large bowl, combine the diced mango, bell pepper, black beans, cilantro leaves, scallions, lime juice, salt and pepper. Mix well and let sit for a few minutes before serving to allow the flavors to fuse together