Combine all marinade ingredients in a blender or use a hand blender and blend until smooth (scraping the sides as necessary).
Place the steak on a large plate or in a baking dish.
Using a fork, poke holes throughout the steak on both sides.
Pour the marinade over the steak and massage it in on both sides.
Let marinate for at least 30 minutes and up to overnight.
To make the breadcrumb salsa
Make the breadcrumbs by heating 1 tablespoon oil in a large skillet over medium heat. Add the diced bread and sautée until golden and crunchy, about 5 minutes.
Combine all the salsa ingredients except for the toasted breadcrumbs in a medium bowl.
Mix well and taste for seasoning. Add more salt and red wine vinegar as necessary.
Set aside until you are ready to serve, then Add the breadcrumbs at the last minute and mix before serving.
To cook the steak
Bring the steak to room temperature if it was refrigerated.
Wipe off excess marinade with paper towels.
Heat your grill on high for at least 5 minutes.
Season the steak well with kosher salt & freshly ground pepper.
Grill the steak over high for about 4 to 6 minutes per side, or until the desired internal temperature is reached (120 to 125° F for medium-rare). Verify with a meat thermometer.
Transfer to a cutting board and let rest for 5 to 10 minutes covered with aluminum foil.
Slice the steak very thin across the grain.
Mix in the breadcrumbs with the prepared salsa and serve over the top of the sliced steak.