In a small bowl, whisk together the mayonnaise, Marukan Genuine Brewed Rice Vinegar, ketchup, Dijon mustard, garlic powder, salt, and pepper until well combined. Set aside.
Divide the beef into 6 equal-sized balls. Flatten the beef onto the tortillas, spreading all the way to the edges. Season with salt and pepper.
Heat a non-stick skillet over medium-high heat. Place the tortillas, beef side down, into the skillet and cook for 2 – 3 minutes. Flip the tortillas over, top with a slice of cheese, cover the skillet, and cook for another 90 seconds or until the cheese is melted.