Preheat your Blackstone griddle. Set one side to medium-high heat (for cooking the meat) and the other side to low heat (for keeping the food warm).
Drizzle the vegetable oil onto the medium-high zone. Add half of the diced white onion (reserve the rest for garnish) and sauté for about 2 minutes until it begins to soften.
Add the ground beef to the onions. Break it apart with your spatula and cook until nicely browned and no longer pink (about 5-7 minutes).
Sprinkle the taco seasoning evenly over the cooked beef and pour in the water. Stir well to combine. Let it simmer for 2-3 minutes until the sauce thickens and coats the meat beautifully.
Scrape the finished taco meat over to the low-heat zone of your griddle to keep it hot and ready for serving.
Place your tortillas on the medium-heat side of the griddle. Toast them for about 30-45 seconds per side until they are warm, pliable, and have a slight, golden crispness. (Tip: toast them right where you cooked the meat to absorb those extra flavors!)
Assemble the tacos! Spoon the hot beef mixture into the warmed tortillas. Top with the reserved raw diced onions, fresh cilantro, and shredded cheese.
Serve immediately with fresh lime wedges on the side.