For the roasted tomato salsa: Position a rack in the middle of the oven and preheat the oven to 450 degrees F. (Or prepare a grill for high heat.)
Line a rimmed baking sheet with parchment paper. Place the tomatoes, onions, jalapeno and garlic on the parchment. Roast for 15 to 20 minutes, then remove the onions and garlic and set aside; peel the garlic. Return the baking sheet to the oven and roast the jalapeno and tomatoes until charred and soft, about 15 minutes more.
(Or, if making on the grill, place the vegetables on a perforated pan or aluminum foil on the hot grill. Cook, covered and turning when necessary, until all the vegetables are evenly charred and soft. The tomatoes and jalapeno will take longer than the garlic and onions, so remove everything as it finishes cooking.)
Transfer all the vegetables to a blender and add the cilantro, chipotles with adobo sauce and salt. Blend on medium speed until a uniform puree has formed. With the motor running, slowly add the oil until emulsified and completely incorporated. If the consistency of the salsa is too thick, add some water 1 tablespoon at a time until the desired consistency is achieved. Taste and adjust the seasonings, adding more chipotle if desired. Let cool before using, or transfer to an airtight container and refrigerate until needed. The salsa will keep for up to 1 week.
For the skirt steak: Season the steak on both sides with salt and pepper. Toss with some of the roasted tomato salsa and marinate, refrigerated, for at least 1 1/2 hours and up to overnight. Reserve the remaining salsa for serving.
For the grilled romaine: 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 some salt and pepper, and gently toss to combine.
Prepare a grill or grill pan for medium-high heat.
Remove the steak from the marinade and let any excess marinade drip off. Grill 4 to 5 minutes per side for medium rare. Let rest for 5 to 7 minutes.
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 again, 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 and toss with the lemon juice. Slice the steaks thin and serve with the reserved roasted tomato salsa and grilled romaine. Serve immediately.
Adapted from "Season with Authority: Confident Home Cooking" by Marc Murphy © Houghton Mifflin Harcourt 2015. Provided courtesy of Marc Murphy. All rights reserved.