Prepare the Potatoes: Preheat the oven to 400°F (200°C). Wash and scrub the Russet potatoes, then poke several holes in each with a fork. Place them directly on the oven rack and bake for 45-60 minutes, or until tender when pierced with a fork.

Cook the Ground Beef: While the potatoes bake, heat a large skillet over medium heat. Add the ground beef and cook until browned, breaking it apart with a spatula. Drain any excess fat.

Season the Beef: Stir in the taco seasoning and water, simmering for 5-7 minutes, until the beef is well-coated and the water has mostly evaporated. Set aside.

Assemble the Potatoes: Once baked, slice the potatoes open and fluff the insides with a fork. Spoon the seasoned ground beef mixture over each potato.

Top with Cheese: Sprinkle shredded cheddar cheese over the beef and return the potatoes to the oven for 5-7 minutes, or until the cheese is melted and bubbly.

Add the Toppings: Remove from the oven and top each potato with sour cream, chopped green onions, and diced tomatoes.

Serve: Serve the Cheesy Taco Potatoes immediately while the cheese is warm and gooey.