Cuban Manchego Cheese Turnovers

Whisk flour and salt together in a bowl. Cut in butter with a pastry blender or 2 knives until the mixture resembles coarse crumbs. Add 1/4 cup water, egg, and vinegar; mix with a fork to combine. Gradually mix in remaining water, adding just enough to bring dough together.

Place dough on a sheet of plastic wrap and knead gently until smooth. Divide the dough in half and shape into balls. Wrap in plastic wrap and chill for 30 minutes.

While the dough is chilling, melt butter in a large skillet over medium heat. Add onion and cook until translucent, about 5 minutes. Add spinach; stir until wilted, 1 to 2 minutes. Remove from heat and allow to cool, about 5 minutes. Stir in Manchego cheese, raisins, and hazelnuts.

Grease 2 baking sheets or line with parchment paper. Beat egg and water in a small bowl.

Remove 1 ball of dough from the refrigerator. Roll dough to 1/8-inch thickness on a lightly floured surface. Cut out circles with a 3-inch cookie cutter. Spoon about 1 tablespoon of the filling into the center of each circle. Brush the edges with egg wash, fold in half to form a pouch, and seal.

Repeat with remaining dough and filling. Place empanadas on the prepared baking sheets and chill for 30 minutes. Reserve any remaining egg wash.

Preheat the oven to 375 degrees F (190 degrees C).

Brush the empanadas with reserved egg wash and bake in the preheated oven until golden brown, about 25 minutes.