Take a square of parchment paper large enough to wrap around the fish.
Place the paper in an 8 x 8-inch (20 x 20 cm) glass dish.
Set the fish on it.
Rub all over with the melted butter.
Pull up the paper to form a sort of open bag.
Add the lemon juice, the vodka or vermouth, salt and pepper to taste.
Place 2 to 3 flowering tops of dill on the fish.
Close the bag by folding the paper together.
Microwave 20 minutes at MEDIUM-HIGH.
Let stand 20 minutes.
Do not open the package.
When cool, refrigerate 12 hours.
The juice will form a sort of jelly.
Serve on a bed of lettuce.
Surround with parsley, alternating with thin slices of lemon and cucumber.