Preheat oven to 350 degrees F (175 degrees C).
Heat the olive oil in a large pot over medium-high heat. Add the beef and cook until browned on all sides, about 5 minutes.
Drain off any excess fat.
Stir in the enchilada sauce and taco seasoning. Bake on 350 1-2 hours, or until the beef is tender and easily shredded.
While the beef is cooking, warm the tortillas in a skillet over medium heat until soft and pliable.
Once the beef is cooked, shred it with two forks.
To assemble the tacos, place a spoonful of shredded beef on each tortilla. Top with shredded cheese.
Fold the tortillas in half and place them on a baking sheet.
Bake for 10-15 minutes, or until the tortillas are crispy and the cheese is melted.
Top with sour cream and lettuce.