Make corn and tomato salad: Cook the corn your favorite way; I use the grill. Heat your grill to a high heat. Shuck the cobs, removing any stringy bits, and lightly oil the cobs. Place directly on the grill and cook until charred spots form, rotating the cobs as needed. This can take about 5 to 10 minutes, depending on how robust your grill is. Set the cobs aside to cool slightly while you make the dressing.
Pour olive oil, cider vinegar, kosher salt, many grinds of black pepper, and minced garlic in a medium-large bowl and whisk to combine. When corn is cool enough to handle (with a towel, if needed), cut the kernels from the cob and add to the dressing in the bowl. Scatter tomatoes, jalapeño, scallions, and herbs on top of the corn in layers, but I don’t bother mixing it at this point. I like the corn to marinate and gently pickle in the dressing while I cook the steak. Do ahead: Corn salad can be made 1 hour in advance. If you’d like to make it even earlier, I’d leave the herbs off until right before serving so they don’t discolor.
Cook the steak: On a grill: Heat your grill to high for 10 minutes before using it. I like my (small, gas) grill as ripping hot as I can get it for a skirt steak, since it’s so thin and I want to get color on the outside before it overcooks in the center. Lightly oil the grill and the steak, cooking for 2 minutes on the first side, then flipping it and cooking it for 2 minutes on the second side for medium-rare. Transfer to a cutting board to rest for 5 to 7 minutes.
On the stove: Heat your heaviest skillet, ideally cast-iron (this is my forever go-to) over high heat for several minutes, until the pan is smoking hot. Lightly coat it with a neutral oil and add the steak. If you had to cut yours into a few segments, you might only be able to cook two at a time. Cook for 2 minutes on the first side, then flip the steak and cook it for 2 minutes on the second side for a medium-rare steak. Transfer to a cutting board to rest for 5 to 7 minutes.
Assemble and serve: Stir tomato-corn salad to mix the ingredients and taste, adjusting seasoning if needed. Once the steak has rested, cut it across the grain into 1/4- to 1/2-inch thick slices. Arrange steak fanned on a serving platter and drizzle any juices that have collected on the cutting board over it. Season lightly with additional salt and pepper. Spoon some tomato-corn salad over it, leaving the rest in a bowl on the side for adding more at the table. Eat right away.
