Cut potatoes in half lengthwise. Slice across into ¼-inch-thick half moons
In mixing bowl, combine tomatoes, water and taco seasoning, reserving 2 teaspoons taco seasoning
Spread 2 tablespoons tomato mixture in bottom of a 1-quart microwave-safe dish
Cover with 4 tortilla halves
Crumble beef over tortillas and sprinkle with reserved taco seasoning
Sprinkle half the cheese over beef. Add half the remaining tomato mixture. Spread potatoes on top in a single layer
Cover with remaining tortillas. Spread remaining tomato mixture on top and sprinkle with remaining cheese
Cover tightly with lid or plastic wrap
Microwave on high for 20 minutes (cooking time may vary depending on your microwave) or until potatoes and beef are done.
Let sit for two minutes. Use oven mitts or tongs to remove from microwave. Remove plastic wrap carefully to prevent burns from steam.