Place the flour, salt and frozen butter into a bowl of a food processor. Pulse process until the butter is in small bits, about 10-15 seconds of processing. Slowly add in the cold water a tablespoon at time, pulsing between additions until the mixture begins to form larger clumps. There should be some bits at the bottom that still look dry, that's okay. The dough should hold together when squeezed with your fingers but should not be sticky. If it is too dry, add more water 1 tablespoon at a time. Transfer the mixture to a large bowl or onto a clean work surface. Use your hands to press the dough together to form a large ball. If there are dry bits at the bottom of the bowl, that's okay, you can leave them there. Separate the dough into two evenly sized discs.

Preheat your oven to 375 F° and prepare your work surface with parchment paper dusted with flour. Roll out each piece of dough into rectangles about ⅛ inch in thickness. In one of the rectangles, use a fork or toothpick to poke holes so air can escape while baking.

Add the filling to the bottom dough leaving about 1 inch of room around the edges. Top with the second dough and seal them together using a fork to crimp the edges. Brush the entire pastry with the “egg wash”.

Place the pop tart on a baking sheet and bake for 30-40 minutes and golden brown. Let cool before stirring together the glaze and pour over the pop tart. Finish with cinnamon if desired. Cut into 12 pieces and serve.