Pour water into a skillet. Place asparagus and onion in the skillet. Bring water to a boil over medium heat. Cover skillet and steam asparagus and onion 2 to 5 minutes, just until slightly tender. Add a few tablespoons of extra water, if needed, to maintain steam.
When water has steamed off, immediately place butter in skillet. Continue cooking until onions and asparagus are lightly browned. Mix in garlic, and continue cooking about 30 seconds. Season with salt and pepper to taste.