Add all purpose flour, whole wheat flour, oats, salt, vital wheat gluten, yeast, pumpkin seeds, cranberries, and orange zest to a large mixing bowl. Mix well to incorporate all the ingredients.
Make a well in the middle of the mixture and pour in the orange juice and 3/4 cup of warm water. Mix until you don't see any more flour. If the mixture feels dry and crumbly, add more water (up to 1/4 cup) until all the flour has been mixed in and you have a shaggy, sticky dough.
Cover the bowl with a towel and let the dough rise for 12-18 hours, or overnight. Place the bowl in a warm place to help the dough rise.
Preheat the oven to 450 degrees. Put the dutch oven (with lid on) into the oven to preheat for 30 minutes. While the pot is heating, uncover the dough. You'll know it's ready because the top of the dough will be covered with tiny air bubbles. Punch the dough down with your fist and fold the dough over itself four times. You might need a sprinkle of flour if the dough is too sticky. Cover the bowl again and let it rise for 30 minutes (while the pot is heating).
Carefully, remove the pot from the oven and remove the lid. Sprinkle wheat bran into the bottom of the pot.
Hold the bowl directly above the hot pot and use a spatula (or your hand) to scrape the dough into the pot. It will sizzle and start to cook, so, quickly replace the lid and put the pot back into the oven.
Bake (covered) for 40 minutes. Remove the lid and check the crust. If you like a dark brown crust then you can remove the lid while it bakes for 5 more minutes. If you like a softer, lighter crust, leave the lid on and continue baking for 5 more minutes.
Carefully remove the bread from the pot and place it on a cooling rack for one hour!