Preheat oven to 160 °C (320°F) with the fan on (see note 1 if you don't have a fan function) and line an 8.5x4.5inch loaf tin (I like to lightly grease the tin before lining it so that the parchment paper sticks better).
In a bowl sift together your flour, cornstarch, baking powder and salt. Using a whisk or fork, mix until well combined. Set aside for now.
In a large bowl add in the butter, vegetable oil, sugar and orange zest. Using a hand or stand mixer on a medium high speed, cream that together for 2 minutes until it's light and fluffy.
Next add in the eggs one at a time, mixing well in between each addition.
Next add in the milk, fresh orange juice and vanilla, and mix until well combined. Once combined, take any remaining batter off of your mixer attachment/s and set aside as the rest of the mixing will be done by hand.
Add the premixed dry ingredients into the wet, and using a spatula gently fold until just combined. Do not overmix (see note 2).
Lastly, coat the cranberries with 1 tbsp of flour (see note 3), and then add them to the batter, discarding any excess flour. Fold them in with a spatula until just combined - do not overmix.
Distribute the batter into the lined loaf tin and level out the top. Drop the cake tin lightly on the counter twice to remove any large air bubbles and bake for 65-60 minutes, or until a skewer or knife inserted into the centre comes out clean (or with a few moist crumbs). If using fresh cranberries, check the bread at 50 minutes and bake further if needed.
Once baked, allow the bread to cool in the loaf tin for atleast 20 minutes, before transferring it onto a wire rack to completely cool.