Don't toss broccoli stalks! If you peel and thinly slice them, you can cook them the way you do florets.
In a large skillet, heat oil over medium-high. Add onion and saute until golden, about 6 minutes. Add garlic, coriander, and red-pepper flakes and cook until fragrant, 30 seconds. Add broccoli, lemon zest, and 2 cups water. Bring to a boil, then reduce heat and cover. Cook until fork-tender, 8 minutes. Season with salt and pepper and serve with lemon wedges.