Ingredients
1 1/4 cups whole wheat flour
1 cup all-purpose flour, plus more for dusting
1/4 cup wheat bran
1/4 teaspoon salt
1/4 teaspoon baking soda
2/3 cup packed dark-brown sugar
1 teaspoon finely grated lemon zest
10 tablespoons unsalted butter, softened
1 large egg
1/4 cup smooth unsweetened applesauce
1 cup raspberry jam
Preparation
Whisk together flours, bran, salt, and baking soda in a medium bowl; set aside. Put brown sugar and zest in the bowl of an electric mixer fitted with the paddle attachment; mix on medium speed until combined. Beat in butter until fluffy. Beat in egg until pale and smooth. Reduce speed to low. Mix in the flour mixture in 3 batches, alternating with the applesauce. Divide dough in half; wrap in plastic. Refrigerate until firm, about 2 hours.
Preheat oven to 375 degrees. Roll out 1 piece of dough between 2 lightly floured sheets of parchment to a 9 1/2-by-11 1/2-inch rectangle, about 1/8 inch thick. If dough becomes too soft, refrigerate until firm. Remove top piece of parchment. Trim dough 1/2 inch on all sides. Transfer rectangle on parchment to a baking sheet.
Cut rectangle in half lengthwise. Spread 1/4 cup jam down half of each length, leaving a 1/2-inch border. Fold dough over; pinch to seal. Refrigerate until firm, about 20 minutes. Repeat with remaining chilled dough and jam.
Cut crosswise into 1 1/2-inch-wide bars, but do not separate until after baking. Bake until golden brown, about 20 minutes. Let cool on sheet on a wire rack. Bars can be stored in an airtight container at room temperature for up to 3 days.
