Take each spear of asparagus and break it towards the end, wherever it naturally snaps. This will ensure that the asparagus won't have any woody ends. Place the asparagus in a microwave-safe container with a lid (preferrably glass). Pour in the water. Roll the lemon on a cutting board or counter to release the juices, then slice in half. Squeese each half, cut side up to keep seeds in, over the asparagus. Sprinkle with pepper and garlic powder, if using.
Cover the dish and place in the microwave. Cook for 5 minutes on High, then let rest for 5 minutes after it has finished cooking. If the asparagus isn't quite tender-crisp, microwave for another minute before serving. Enjoy!
Thhis dish is also great with a splash of white wine in kplace of some of the water.