- 1 lemon
- 2 small heads of broccoli, cut into 2″ florets
- Kosher salt
- 4 carrots, peeled, halved lengthwise
- 2 medium white onions, each cut into 6 wedges with some root attached
- 1 12-ounce bunch asparagus, trimmed
- 1 fennel bulb, trimmed, cut into 8 wedges with some core attached
- 2 cups low-salt chicken broth
- 1 vanilla bean, split lengthwise
- 3 tablespoons olive oil, divided
- 4 garlic cloves, crushed
- 10 coriander seeds
- 5 whole black peppercorns
- 4 sprigs thyme
- 1 bay leaf
- 1 teaspoon (or more) Sherry vinegar
- Freshly ground black pepper
- Fresh cilantro leaves
- Using a small sharp knife, cut all peel and white pith from lemon; discard. Cut flesh crosswise into 1/4″-thick slices; set aside.
- Line a large rimmed baking sheet with a kitchen towel. Cook broccoli in a large pot of boiling salted water for 1 minute. Using a slotted spoon, transfer to prepared sheet. Repeat in same pot with carrots, onions, asparagus, and fennel, returning water to a boil between batches.
- Place chicken broth in a small saucepan over low heat and scrape in seeds from vanilla bean; add bean. Bring to a simmer. Remove from heat; let infuse for 10 minutes.
- Heat 1 tablespoon oil in a large pot over medium heat. Add carrots, onions, fennel, and garlic; cook for 1 minute. Add coriander, next 3 ingredients, and infused broth with bean. Cover with lid slightly ajar; simmer until vegetables are crisp-tender, 12-15 minutes. Stir in broccoli and asparagus.
- Using a slotted spoon, transfer vegetables to a warm serving dish. Bring broth to a boil and cook until reduced to 1 cup. Remove broth from heat; whisk in remaining 2 tablespoons oil and 1 teaspoon vinegar. Season with salt, pepper, and additional vinegar, if desired. Pour sauce over vegetables. Garnish with lemon slices and cilantro.