For the marinade, whisk the yogurt, cilantro, tomato paste, garlic, ginger, lemon juice, brown sugar, coriander, cumin, turmeric, cardamom, chili powder, salt and pepper together until well blended.
For the skewers: Thread the salmon pieces and peppers onto the skewers, using 5 pieces of salmon for each skewer and 4 each of the peppers, alternating them so the peppers are between the pices of salmon. Place them in a dish that will accommodate them in a single layer and pour over the marinade. Turn the skewers a few times, making sure they are well coated, cover with plastic wrap and place in the refrigerator to marinate for at least 1 hour.
Preheat an indoor grill or a barbecue grill to medium-high heat. Oil the grill, remove the skewers from the marinade and sprinkle them with salt. Place on the grill and cook 5 minutes, turning halfway through cooking. Skewers are done when the fish is firm and slightly charred.