Heat oven to 425F. Squeeze the lemon into a wide,
shallow dish, and
top with cold water. Peel and core apples, then cut in half. Immerse
apples in lemon water.
Place puff pastry on a large baking sheet. Use a sharp knife to
lightly score a half-inch border; do not cut all the way through.
(This will allow a frame of pastry to rise above the apple filling.)
Refrigerate until needed.
Pat apples dry, and cut each half into quarters. Slice each quarter
thinly. Remove pastry from refrigerator, and sprinkle with 1
tablespoon sugar. Working inside scored lines, place neat rows of
closely overlapping apples, until pastry is covered.
Brush apples with melted butter, and sprinkle with remaining sugar.
Bake until pastry puffs around apples and fruit is soft and lightly
colored, 20 to 25 minutes. Serve warm.