Prepare the cranberry filling: In a food processor, pulse the whole cranberries until they’re ground and pebbly, but not completely pureed, scraping the machine down once or twice. In a small bowl, combine the brown sugar and cinnamon. Set both aside.
Switch to a dough hook (or turn out onto a lightly floured surface) and mix on medium speed for 8 minutes or knead by hand for approximately 10 minutes, until the dough is soft, pliable, and slightly tacky but not sticky. Place the dough in a lightly oiled large bowl, cover with plastic wrap, and let rise at room temperature for approximately 2 hours, until the dough doubles in size. To check dough readiness, gently press the dough with two fingers. If the indent stays, the dough is ready.
Heat the buttermilk and 1/4 cup orange juice squeezed from the zested orange to the temperature specified by the yeast manufacturer (120 to 130 degrees F for Red Star Platinum). If the buttermilk separates, simply whisk it back together. Pour the liquid into the dry ingredients, mix on low speed (or mix by hand with a wooden spoon) until the ingredients come together and form a ball.
In the bowl of a standing mixer fitted with the paddle attachment or a large mixing bowl, stir together the all-purpose flour, white whole wheat flour, vital wheat gluten, yeast, and salt. Add the butter, egg, and orange zest.