- 1/4 medium white onion, quartered
- 1 small tomatillo, husk removed
- 1 jalapeño, sliced, seeds removed
- 1 garlic clove
- 1/4 avocado, chopped
- 1/4 cup chopped fresh cilantro leaves
- 1/4 cup olive oil
- 1 tablespoons fresh lime juice
- Kosher salt
- Freshly ground black pepper
- 1 small poblano chile
- 2 heads of romaine lettuce, outer leaves removed, halved lengthwise
- 2 tablespoons olive oil
- Kosher salt
- 1 avocado, chopped
- 1/4 medium white onion, finely chopped
- 1 tablespoons fresh lime juice
- 2 ounces Cotija cheese, finely grated
- 1 tablespoons chopped cilantro stems
- Bring onion, tomatillo, jalapeño, garlic, and 2 cups water to a boil in a small saucepan. Reduce heat and simmer until onion is very tender, 6–8 minutes; let cool. Drain, reserving cooking liquid.
- Purée onion mixture with avocado and cilantro leaves in a blender. With motor running, gradually add oil and 2 tablespoons cooking liquid and blend until combined.
- Add lime juice; season with salt and pepper.
- Prepare grill for medium-high heat. Grill poblano, turning occasionally, until charred and blistered, 6–8 minutes. Let cool. Peel and finely chop.
- Drizzle cut sides of romaine with oil; season with salt. Grill, cut side down, until charred, about 3 minutes. Turn and grill just until warmed through, about 30 seconds.
- Spoon dressing onto plates and top with romaine, charred side up, avocado, onion, and poblano. Drizzle with lime juice; season lightly with salt. Scatter Cotija cheese and chopped cilantro stems over.