Cream butter and salt first. Add almond meal and starch – mix to smooth. Add the egg and vanilla. Use at room temperature.
Cut the apples in half and remove the core and stem using a melon baller or a knife. Slice out thinly and soak them in lemony water. Meanwhile, bring 3 qt/3L of water to boil and blanch apple slices for about a minute to soften. Transfer in ice water and drain over paper towels; set aside. Flatten out puff pastry and divide into 6 thin strips; 21''/53cm long x 2.5''/6cm wide. Spread some almond cream and overlap apples leaving an extra pie crust at the bottom. Fold extra dough over to hold apples slices in place. Cut in half and make two roses. Repeat these steps until done. Place tarts in a greased 12-cup muffin pan.
Bake tarts at 375ºF/190ºC for about 50 minutes. Dust with powdered sugar and cinnamon; bake for 10 minutes more. Serve at room temperature or just warm. Enjoy!