Soak the cranberries in orange juice for 10 minutes and then drain them. Toss the cranberries in some of the flour blend. Zest and juice the oranges.
Preheat your oven to 350°F (175°C). Line a 9x5 inch loaf pan with parchment paper
In a medium bowl, whisk together the millet flour, sorghum flour, tapioca starch, baking powder, baking soda, and salt.
In a large bowl beat the butter, sugar and orange zest until lighter in colour and creamy. Beat in the eggs one at a time and add the orange juice.
Add the ingredients to the wet ingredients, stirring just until combined. Be careful not to overmix.
Gently fold in the cranberries.
Pour the batter into the prepared loaf pan, spreading it evenly.
Bake for 55 to 60 minutes, or until a toothpick inserted into the centre comes out clean.
Let the loaf cool in the pan for about 10 minutes, then transfer it to a wire rack to cool completely before adding the frosting and slicing.