Preheat oven to 400°F. Line a baking sheet with aluminum foil.

Place potatoes on the baking sheet, drizzle with 1 tablespoon olive oil, and sprinkle with ½ teaspoon salt. Roast for 60-75 minutes until fork-tender.

While the potatoes are baking, cook the ground beef with diced onion in a skillet over medium-high heat until browned, about 5-6 minutes. Drain excess fat.

Add taco seasoning and water to the skillet. Stir well, bring to a low boil, then simmer for 3-5 minutes until sauce thickens.

Remove baked potatoes from oven, let cool for 5 minutes. Cut a slit down the center of each and gently push ends to open them.

Fluff inside of each potato with a fork and scoop out 1-2 tablespoons to make space for filling.

Fill each potato with seasoned ground beef. Top with shredded cheddar, diced tomato, guacamole, sour cream, cilantro, and green onion slices as desired.