Cut the plums into 1/4-in-thick slices.
Put the butter and sugar in a bowl, and cream with a whisk. Beat the egg in a separate bowl and add little by little to the big bowl. Mix to combine. Then add almond powder and mix.
Preheat the oven to 200℃/400℉. On a baking paper, roll out the dough until roughly a circle. Transfer the dough with baking sheet onto the baking tray.
Spread the almond cream evenly onto the center of the dough and arrange the plum slices on top. Sprinkle cane sugar over the plums.
Carefully fold the edges up and over the filling. Overlapping the dough slightly. Brush the edges with egg wash.
Bake at 180℃/350℉ for about 45 -60 min or until the crust gets golden brown and crispy. Remove from the oven and let cool for 5 minutes before transferring to a cooling rack. You can brush apricot jam on top. (Check "Helpful Tips".)
Serve warm with a scoop of vanilla ice cream.