Clean the mushrooms, separate the caps from the stems, and keep the latter aside for another time.
Arrange the caps in a baking dish lined with aluminum foil and place in a preheated oven at 160°C (350°F) long enough for the vegetation water to evaporate. If the capsules were very large, score the cap with a knife.
As soon as they are ready, transfer them to a pan where you have allowed the butter to melt and let them season by adding tarragon, salt and pepper.
After 20 minutes, drizzle with lemon juice, let it evaporate, and serve.
Notes
For an even more aromatic touch, you can add a pinch of dried herbs along with tarragon. This dish pairs perfectly with a dry white wine. Remember to carve the mushroom caps if they are particularly large, to encourage even cooking.