Dice fresh (or canned) peaches (no need to peel them). Toss them with the lemon zest and juice, cinnamon, almond extract, brown sugar and cornstarch.
On a floured surface, roll out puff pastry to a square. Cut it into 8 smaller squares. Brush the edges of each square with the egg wash. Place about a little bit of peach mixture on each square. Fold one corner of the dough over to form a triangle. Press the edges with a fork to seal them.
Serve Peach Turnovers sprinkled with powdered sugar.