Trim asparagus by cutting off the bottom, light-colored part of the stem, leaving the top 6 inches or so. (Make the cut on a diagonal for a prettier presentation if desired.) Discard the bottom parts.
Place trimmed asparagus in a steamer insert or colander placed in a saucepan with about 1/2 inch of water. Cover with a lid and heat over medium high heat. Once the water starts to boil, turn to medium-low and steam until crisp-tender, about 5 minutes. (It will continue to cook as it stands.)
Remove the steamer and empty the saucepan. Transfer asparagus to saucepan and toss with butter to melt and coat. Add salt, pepper and optional red pepper flakes. Toss again.
If desired, add fresh herbs like chives, dill, tarragon, lemon balm, rosemary or basil. Serve warm or at room temperature.