Preheat your oven to 400°F. In a bowl, toss the broccoli and garlic with olive oil, salt, black pepper, onion powder, and red pepper flakes.
Spread the mixture in a single layer on a rimmed baking sheet and roast for 20 minutes, stirring halfway through until the edges are charred.
Remove from the oven, toss with lemon zest, and serve warm. Garnish with Parmesan if desired.