Spiced Salmon Kebabs with Yogurt Sauce

Name: Spiced Salmon Kebabs with Yogurt Sauce
Ingredients: 1 teaspoon cumin seeds; 1 teaspoon coriander seeds; 2 cardamom pods; 3 cloves; 1 cinnamon stick; 1 cup Greek yogurt; 1/2 small red onion, finely chopped; 1 tablespoon fresh lemon juice; 1 teaspoon fresh lemon zest; 1 teaspoon cayenne pepper; 1 (2-pound) fillet salmon, cut horizontally into 1-inch thick slices; Olive oil, for drizzling; Salt and freshly ground pepper; 12 -inch wooden skewers, soaked in water for 30 minutes; 1/2 orange