Position a rack in the center of the oven and heat the oven to 400ºF.
In a medium bowl, mash the goat cheese with a fork. Add the chives, onion, lemon zest, 1/2 tsp. kosher salt, and 1/4 tsp. pepper. Stir until well combined.
On a lightly floured surface, unfold the pastry sheet and lightly dust with flour. Use a rolling pin to roll the sheet into a 12-inch square. Cut the dough into 9 squares. Put equal amounts of the filling (about 1 Tbs.) onto the center of each square. Moisten the edges of a square with a fingertip dipped in water. Fold the dough over to form a triangle, gently pressing to remove air pockets around the filling and pressing the edges of the dough together. Use the tines of a fork to crimp and seal the edges of the turnover. Repeat this process with the other dough squares.
Arrange the turnovers on a cookie sheet and bake until the turnovers are puffed and golden all over, 15 to 18 minutes. Let them cool on a rack for a few minutes and serve warm.
Make Ahead Tips
The turnovers may be filled and shaped up to 2 hours ahead of cooking. Cover tightly with plastic wrap or brush with melted butter before refrigerating.
nutrition information (per serving):
Photo: Scott Phillips