BBQ or Gas Grill,
Bring the Fullblood Wagyu underblade roast out of the freezer, and place it in the refrigerator 24 to 48 hours before starting this recipe.
PREPARING THE MARINADE
Combine the yogurt, olive oil, red wine vinegar, chopped oregano, chopped garlic, kosher salt, and black pepper in a blender. Blend until smooth. This is your yogurt marinade.
Put the Fullblood Wagyu underblade roast in a Ziploc bag, and pour the yogurt marinade over the roast.
Seal the bag, and place it in the refrigerator for 12 to 24 hours.
PREPARING THE FULLBLOOD WAGYU UNDERBLADE ROAST
Pull the marinated Fullblood Wagyu roast from the refrigerator, and allow it to sit at room temperature for 1 hour before cooking.
Preheat the oven to 450°F. Remove the roast from the marinade, and let the marinade drain off (do not rinse the marinade off).
Place the roast on a roasting rack. Cook at 450°F for 20 minutes.
Reduce the temperature to 325°F, and roast for 50 minutes (for a rare finish) or 75 minutes (for a well done finish).
While the roast is in the oven, make the tzatziki sauce.
Check the roast with a probe thermometer for a temperature of 120°F to 125°F (for a medium-rare finish).
PREPARING THE TZATZIKI SAUCE
Mix all of the sauce ingredients (Greek yogurt, minced garlic, lemon zest and juice, olive oil, horseradish, and grated cucumber) in a medium bowl.
Place the bowl of sauce in the refrigerator until ready to use.
PREPARING THE GRILLED ONIONS AND PITA BREAD
Cut off both ends of the onions, and remove the peel.
Cut the onions into half-inch rings.
Heat a BBQ or gas grill on medium-high heat.
Grill the onions until they have wilted and have grill marks on them. Set aside.
Grill the pita bread on the hot grill for 1 minute per side (just to get the grill marks on the bread). Don’t leave them on the grill too long, or they will be tough.
Remove the Fullblood Wagyu underblade roast from the oven, and let it rest for 10 to 15 minutes.
Slice the roast against the grain into thin, 1-inch strips.
Serve warm on the grilled pita bread with the tzatziki sauce, grilled onions, watercress, mint leaves, and cherry tomatoes.