Cook cumin seeds through ground red pepper in a small skillet over medium-high heat, shaking pan occasionally, until spices begin to smoke. Transfer mixture to a coffee grinder or a mortar; grind.
Combine ground spices, salt, and olive oil in a small bowl; spread over salmon fillets. Cover and chill 1 1/2 to 2 hours.
Cut 6 (10-inch) lengths of heavy-duty aluminum foil. Fold each 2 or 3 times to fit the size of the fillet. Place each fillet, skin side down, on foil sheet.
Prepare a hot fire by piling charcoal on one side of grill, leaving other side empty. (For gas grills, light only one side.) Place rack on grill. Arrange food over unlit side. Grill, covered with grill lid, 15 minutes or until fish flakes with a fork. Slide spatula between skin and flesh of fillet; transfer fillet to plate, leaving skin behind. Top with Cucumber Raita and julienne strips of cucumber. Serve immediately.