Place a greased oven tray in the oven. Preheat the tray and oven to 200°C fan forced.
Combine Cajun spice, paprika, garlic, oregano and pepper together. Sprinkle over all sides of the salmon, pressing it on with fingertips. Heat oil in a frying pan over medium heat and cook salmon in two batches for 1 minute each side until seared. Transfer to the hot oven tray and bake for 8 minutes for medium or until cooked to your liking.
For the salad; whisk yoghurt, lime juice, mustard and oil together in a medium bowl. Thinly slice the fennel, then cut into matchsticks. Add to the yoghurt and stir to coat. Peel and slice the mangoes and stir into the fennel with herbs, season.
Spoon the salad onto serving plates, top with salmon and serve with lime wedges.