Preheat the oven to 425°F with a rack in the center position.
Trim the stalks and flat root base away from the fennel bulbs, reserve the fronds for garnish. Halve and cut into ⅓-inch wedges.
Spread the wedges out on a large rimmed baking sheet. Drizzle with the olive oil. Sprinkle all over with the garlic powder, and salt, toss to combine.
Roast the fennel until tender and beginning to brown, about 20 minutes. Turn on the broiler and cook for another 2 minutes, until the edges are caramelized.