You can also try these tarts with firm, ripe pears instead of apples.
On a floured work surface, roll dough to a 6-by-14-inch rectangle. Dot upper two-thirds of dough with butter and fold dough in thirds, like a letter, starting with the unbuttered portion. Roll dough to a 6-by-14-inch rectangle; refrigerate on a baking sheet until firm, 1 hour (or up to 1 day). Cut dough crosswise into 4 equal rectangles. Place dough on sheet lined with parchment.
Preheat oven to 375 degrees. In a large bowl, gently toss together lemon juice, flour, brown sugar, salt, 1/4 teaspoon cinnamon, and apples. Leaving a 1/2-inch border, arrange apples over dough, overlapping slightly.
In a small bowl, combine egg yolk with 1 teaspoon water. In another small bowl, combine granulated sugar and 1/8 teaspoon cinnamon. Brush edges of dough with egg wash and sprinkle them with cinnamon-sugar mixture. Bake until crust is golden brown and apples are soft, 30 to 35 minutes. Serve warm, topped with ice cream if desired.
For a brunch pastry, cut dough in half before adding apples; serve with sweetened yogurt.