Spiced Roasted Halibut with Fennel and Onion

Name: Spiced Roasted Halibut with Fennel and Onion
Ingredients: 1 1/2 tsp. ground cumin; 1 1/2 tsp. chili powder; 1 tsp. ground cinnamon; 1/4 tsp. ground turmeric; 1 large fennel bulb, cut lengthwise into 1-inch (2.5-cm) wedges; 1 large red onion, halved lengthwise, then cut lengthwise through the root end into 1/2-inch (12-mm) wedges; 3 Tbs. olive oil, plus more as needed; Coarse kosher salt and freshly ground pepper, to taste; 2 halibut fillets, each about 6 oz. (185 g); Chopped fresh cilantro for garnish