Preheat oven to 375 degrees F. Line a baking sheet with parchment paper and set aside.
In a large skillet, heat the olive oil over medium-high heat. When hot, add in the ground beef, taco seasoning, and onions. Cook for about 5-7 minutes, breaking up the meat as it cooks, until the beef is browned. Drain fat, as needed.
Stir in the diced tomatoes and cilantro and cook for an additional 3-5 minutes. Season with salt & pepper to taste and remove from the heat.
Lightly spread olive oil on both sides of the tortillas and place on the prepared baking sheet. Spoon about 1/3 of the ground beef mixture onto one side of each tortilla and sprinkle cheese on top. Fold the other side over and bake the tacos for 12-15 minutes, and broil on high for 2-3 minutes until the cheese is melted and the tortillas are golden brown.
Serve the tacos topped with your favorite toppings and enjoy!