1. Preheat broiler.
2. Prepare the lobster tail for cooking, by removing the soft part with scissors.
3. Make the lobster tail lie flat by hitting the hard shell slightly with mallet or cleaver.
4. Take a skillet, and melt butter in it.
5. Add ginger, mustard, tarragon and salt to it.
6. Spread the mixture on the tails.
7. Allow the mixture to stand for 20 minutes.
8. Broil about 4 inches from heat for 10-15 minutes with meaty side up.
9. Frequently baste.
10. Serve broiled tarragon lobster hot with lemon garnish.