Spinach-Feta Turnovers

In a medium skillet, heat oil over medium; add onions and garlic. Cook, stirring occasionally, until tender, 5 to 7 minutes. Transfer to a large bowl; mix in spinach, feta, lemon juice, and cayenne. Season filling with salt and pepper, and set aside. (Feta can be quite salty, so be sure to taste the filling before adding more seasoning.)

Preheat oven to 375 degrees, with racks in upper and lower thirds. On a lightly floured work surface, roll out each portion of dough (still folded in thirds) into a 12-inch square; cut each into quarters to form a total of 8 equal squares.

Dividing evenly, spoon filling onto center of each of the 8 squares. Lightly brush two adjoining edges of each square with some egg wash. Fold these edges over filling to form a triangle; press firmly to seal (dough should be tightly pressed around filling). With a floured fork, crimp edges.

Transfer turnovers to two baking sheets; brush tops with remaining egg wash. Bake until golden and puffed, 35 to 40 minutes, rotating sheets halfway through.