Apple Pie Breakfast Pastry

Name: Apple Pie Breakfast Pastry
Ingredients: 1 medium Granny Smith apple , peeled, cored and finely chopped (about 1 cup); 3 tablespoons water , divided; 1 teaspoon grated lemon zest; 1 teaspoon lemon juice; ½ teaspoon cornstarch; ½ teaspoon apple pie spice; ¼ teaspoon salt , divided; 1 (8.4-ounce) sheet frozen puff pastry , thawed; All-purpose flour , for work surface; 4 ounces reduced-fat cream cheese , softened; ¼ cup confectioners' sugar plus 1 tablespoon, divided; 1 large egg; 2 teaspoons whole milk