Before you toss this steak on the grill and cook it to crispy, juicy perfection, marinate it in a bright and tangy chimichurri sauce overnight. Top with a few quick-to-make pickled red onions, fresh cilantro, and crumbled cotija cheese for an impressively tasty—not to mention protein-rich—taco dinner.
To make the pickled onions, combine the red wine vinegar, water, sugar, cloves, bay leaf, salt, black pepper, ½ teaspoon dried oregano, and ¼ teaspoon red pepper flakes in a heavy saucepan. Bring to a boil over medium-high heat, then add the red onion slices. Let the mixture come back to a boil, reduce the heat to medium-low, and cook until the onions soften, 3 to 4 minutes. Cover, and set aside to cool completely, or refrigerate in an airtight container for up to 2 weeks.
When you’re ready to cook the steak, strain out the onions from the vinegar mixture and reserve ½ cup of their juice. Combine it with the olive oil, cilantro, parsley, garlic, 1 tablespoon dried oregano, and 1 teaspoon red pepper flakes. In a ziplock bag or large bowl, toss it well with the steak. Marinate at room temperature for 30 minutes, or covered in the refrigerator overnight.
Turn your grill to medium-high heat, and cook the steak for 2 to 3 minutes per side, flipping only once (the steak should pull cleanly from the grill grates when ready to flip). Remove from the heat, and let it rest for 5 minutes before slicing thinly against the grain.
Set each tortilla directly over a burner (or directly on the grill) on medium-high heat, and toast for 1 or 2 minutes per side, until lightly charred. Fill them with steak, and garnish with cotija cheese, some of the pickled onions, and cilantro.