Preheat the oven to 400°F (200°C). Line a baking dish with parchment paper.
In a skillet over medium heat, brown the ground beef. Break it apart as it cooks.
Stir in diced onion and cook until soft. Add garlic and cook 30 seconds.
Mix in taco seasoning and water. Simmer until thick and juicy (about 3–4 minutes).
Lightly spray taco shells with oil for extra crispiness.
Fill each shell halfway with beef mixture.
Add a generous layer of mozzarella and cheddar.
Sprinkle a little cilantro inside.
Arrange tacos snugly in a baking dish so they stay upright.
Bake 10–15 minutes until cheese is fully melted and edges turn golden and crispy.
Broil 1–2 minutes for extra bubbly, browned cheese if you want that next-level crust.
Let them cool slightly before serving.
