Preheat the oven to 350. Set your oven rack to the lower third of the oven. Line your 8x4 loaf pan with parchment, making sure it overhangs on the sides so that it becomes easier to remove your bread after it's baked.
Mash the bananas in a bowl. Add eggs, vanilla, sugar and oil. Whisk well until thick, off-white in colour and well blended.
Sprinkle salt, baking soda, baking powder and cinnamon on top of the batter. Whisk it in well.
Next, add the whole wheat flour. Fold it in gently but ensure it's well incorporated. When the flour is about 75% incorporated, stir in your additions, if using and finish folding; fold only until incorporated and avoid overmixing. Pour into the prepared pan. Run a wet butter knife in the middle of your loaf. This will make it look better and "break" in a more controlled manner.
Bake in preheated oven for 55-65 minutes (60 mins usually works for me) until the toothpick inserted in the centre comes out clean. The best way to test for doneness is with a digital thermometer inserted at 45° angle in the centre of the loaf - for a perfect loaf the internal temperature should be 202-206. My bread took 59 minutes and came out at 204°. It was perfect!
You can cool your bread on wire racks, or do what I do and cool it slightly in the pan for 15 minutes, then remove from the pan and wrap tightly with the plastic wrap. Cool in the fridge or at room temperature. This trick helps trap the steam and keep your bread extra moist!