For the steak: In a shallow nonreactive bowl that is large enough to hold the steak, combine the sherry, sherry vinegar, red onion, garlic, and olive oil. Stir to blend well. Lay the steak in the marinade and turn so that it is coated on both sides. Wrap the bowl loosely in plastic wrap and refrigerate overnight, turning the steak occasionally.
Preheat a grill to high.
Remove the steak from the marinade (discard the marinade), and season the steak with the salt and pepper. Grill the steak for 4 to 5 minutes per side for medium-rare. Remove it from the grill and let it rest for 5 minutes. Then thinly slice the steak across the grain to serve.
For the chimichurri: Combine the olive oil, vinegar, lemon juice, parsley, basil, garlic, shallots, and oregano in a food processor, and pulse until well blended (do not puree). Stir in the kosher salt, black pepper and crushed red pepper. Transfer the sauce to a non-reactive bowl, cover it with plastic wrap, and set it aside for at least 2 hours and up to 6 hours at room temperature. (The sauce will keep in an airtight nonreactive container in the refrigerator for up to 3 days.)
For the piperade: Combine the olive oil, parsley, oregano, garlic, vinegar and crushed red pepper in a small bowl with a whisk.
Heat the vegetable oil in a large saute pan over medium high heat add the onions and cook stirring until softened, about 5 minutes. Add the bell peppers, salt and the black pepper and continue to cook, stirring as needed until tender, about 5 minutes longer. Remove from the heat.
Transfer the peppers and onions to a mixing bowl and toss with the herb mixture. Season with additional salt and pepper to taste.
For the potatoes: Stir the olive oil, garlic, and rosemary together in a small bowl and let it sit at room temperature for at least 15 minutes for the flavors to infuse.
Preheat a grill to medium-high.
Place the potatoes in a pot of salted water and bring to a boil. Reduce the heat to a simmer and cook until the potatoes are tender when pierced with the tip of a knife, about 12 minutes. Drain the potatoes, discarding the water.
Using a towel wrapped around the palm of your hand, gently smash each potato until the skin breaks, while trying to keep the potato whole (leaving it about 1 inch thick). Transfer the potatoes to a baking sheet. Generously brush both sides of the potatoes with the olive oil mixture, and season both sides with the salt and pepper.
Place the potatoes on the grill and cook until grill marks appear and the potatoes are nicely caramelized, 3 to 4 minutes per side.
Emeril Lagasse, Emeril at the Grill: A Cookbook for All Seasons, HarperStudio Publisher, New York, 2009, courtesy MSLO, Inc.