For the pastry, place the flour, sugar, and salt in the bowl of a food processor fitted with a steel blade. Pulse a few times to combine. Add the butter and toss quickly with your fingers to coat each cube of butter with the flour. Pulse 12 to 15 times, or until the butter is the size of peas. With the motor running, add the 1/4 cup ice water all at once through the feed tube. Keep hitting the pulse button to combine, but stop the machine just before the dough comes together. Turn the dough out onto a well-floured board and form into 2 disks. Wrap the disks with plastic and refrigerate for at least one hour.
Preheat the oven to 450 degrees.
Roll each pastry disk into an 11-inch circle on a lightly floured surface. Transfer them to 2 baking sheets lined with parchment paper.
For the filling, peel, core, and quarter the pears. Cut each quarter into big chunks. Toss the chunks with the orange zest. Divide the pear chunks between the pastries, covering the dough and leaving a 1 1/2-inch border. Sprinkle 1 tablespoon of cranberries over the top of each tart.
Combine the flour, sugar, salt, cinnamon, and allspice in the bowl of a food processor fitted with a steel blade. Add the butter and pulse until the mixture is crumbly. Pour into a bowl and rub it with your fingers until it starts holding together. Sprinkle evenly over the top of the two tarts. Gently fold the border of each tart over the pears, pleating it to make a circle.
Bake the crostatas for 30 minutes, or until the crust is golden and the pears are tender. Let the tarts cool for 5 minutes, then use 2 large spatulas to transfer them to wire racks.