2 large (or 4 small) heads romaine lettuce, halved lengthwise, cores left intact
3 tablespoons olive oil, plus more as needed
Freshly ground black pepper
¼ cup fresh lemon juice (from about 2 lemons)
To clean the romaine, place the halves in a large bowl (or several bowls) filled with cold water. Swoosh the lettuce gently in the water and let it sit for 10 minutes— the dirt and grime will settle to the bottom of the bowl. Gently lift the lettuce out of the water and rinse the bowl. Repeat the cleaning process until the water remains clean after you’ve swished the leaves around in it. Gently pat the lettuce dry around and between the leaves to remove as much moisture as possible. Rinse and dry the bowl, and place the lettuce back in it. Season the lettuce with the olive oil and salt and pepper to taste, and gently toss to combine.
Heat a grill or preheat a grill pan over medium to medium-high heat.
Place the romaine halves on the grill, cut side down, and grill until well marked, about 2 minutes. Rotate the romaine 45 degrees and grill until well marked, 2 minutes more. If doing this on a grill pan, you may need to work in batches. Transfer the romaine halves to a cutting board and chop them into 2-inch pieces. Place the romaine in a large bowl, toss with the lemon juice, and serve immediately.