Whole-Wheat Date Bars

Make filling: Bring dates and cider to a boil in a saucepan over medium-high heat.
Reduce heat to medium; simmer until dates are soft and almost all liquid has reduced, about 10 minutes.
Let cool completely.
Transfer to a food processor.
Puree date mixture until smooth.
Make dough: Whisk together both flours, bran, salt, and baking soda in a bowl.
Put brown sugar and zest in the bowl of an electric mixer fitted with the paddle attachment.
Mix on medium speed 30 seconds.
Add butter; mix until combined, about 1 minute.
Add egg; mix until fluffy.
Add flour mixture in three batches, alternating with two batches of applesauce.
Divide dough in half.
Wrap each half in plastic; shape into a rectangle.
Refrigerate until firm, about 2 hours.
Preheat oven to 375F.
Roll out one piece of dough between two lightly floured sheets of parchment paper to a 9 1/2 by 13-inch rectangle.
Dust with more flour, if needed.
Remove top piece of parchment.
Trim dough to a 9 by 12-inch rectangle.
Transfer rectangle on parchment to a baking sheet.
Cut rectangle in half lengthwise.
Spread a heaping 1/4 cup filling down half of each length, leaving a 1/4-inch border.
Fold dough over; pinch to seal.
Refrigerate until firm, about 20 minutes.
Repeat with remaining chilled dough and filling.
Bake until golden brown, about 20 minutes.
Let cool on sheets on wire racks 5 minutes.
Cut into 1 1/2-inch bars.
Transfer bars to wire racks using a spatula; let cool.
Bars can be stored in airtight containers at room temperature up to 3 days.