Although it's tempting to just toss the garlic into the blender without chopping it first, give it a quick chop so you don't end up with big chunks in your dressing. (We learned the hard way!)
5 teaspoons olive oil, divided
1/4 teaspoon cayenne, or to taste
2 hearts of romaine, halved lengthwise
1/4 cup plain nonfat yogurt
1 tablespoon lime juice, or more to taste
1/2 ripe avocado
1/2 teaspoon finely chopped garlic
2 tablespoons chopped cilantro
1/4 teaspoon kosher salt
1/4 cup crumbled cotija cheese*
1/4 cup thinly sliced green onions
How to Make It
Heat a grill to medium (350° to 450°). In a small bowl, combine 1 tbsp. oil with the cayenne. Rub romaine with oil mixture. Grill, turning once, until slightly softened and streaked brown, 5 to 6 minutes total. Arrange romaine cut side up on a platter.
Whirl remaining 2 tsp. oil, the yogurt, lime juice, avocado, garlic, cilantro, salt, and 2 1/2 tbsp. water in a food processor until smooth. Spoon dressing over romaine and sprinkle with cheese and green onions.