In a large skillet, heat 1 tablespoon of cooking oil over medium heat. Add the diced onion and sauté until it becomes translucent, about 3-4 minutes. Next, add the ground beef to the skillet, breaking it apart with a spatula. Cook until browned, approximately 5-7 minutes. Drain any excess fat.
Sprinkle the taco seasoning over the cooked beef and onion mixture. Stir well to combine, ensuring that the meat is evenly coated.
In a separate skillet, heat the remaining 2 tablespoons of cooking oil over medium heat. Lightly fry each corn tortilla for about 10-15 seconds on each side to soften them up.
Preheat your oven to 375°F (190°C). Pour a thin layer of enchilada sauce into the bottom of a 9x13 inch baking dish. Take a tortilla, spoon a generous amount of the beef mixture onto it, and sprinkle with a bit of shredded cheddar cheese. Roll the tortilla tightly and place it seam-side down in the baking dish. Repeat this process with the remaining tortillas and filling.
Once all the enchiladas are assembled in the baking dish, pour the remaining enchilada sauce over the top. Sprinkle the remaining shredded cheese evenly over the sauce.
Cover the baking dish with aluminum foil and bake in the preheated oven for 20 minutes. Then, remove the foil and bake for an additional 10 minutes, or until the cheese is bubbly and slightly golden.
Once the enchiladas are out of the oven, let them cool for a few minutes. Serve topped with freshly chopped cilantro and pico de gallo for a burst of freshness.