Preparation

• Preheat the oven to 400°F. Place a large sheet pan on the middle rack as the oven preheats.
• Cook the ground beef: Set a large skillet over medium-high heat and add the ground beef. Cook, breaking up the meat with a wooden spoon, until cooked through, 5 to 6 minutes. Stir in the taco seasoning and water and bring to a boil. Reduce the heat to a simmer. Cook, stirring often, until thickened, about 4 to 5 minutes.
• Assemble tacos and serve: Remove the skillet from heat and stir in the cheese. Cover half of each tortilla with the ground beef mixture and fold in half. Carefully remove the sheet pan from the oven and add the folded tacos. Bake until golden brown on the first side, about 5 minutes, then flip and bake again until golden on the other side, about 4 more minutes.
• Serve with onion, tomatoes, and lettuce for topping along with salsa, sour cream, and guacamole.