Preheat oven to 180°C. Line a 12-cup muffin tin with liners.
Melt butter in a large bowl in the microwave. Set aside to cool.
Once butter has cooled, zest orange into the same bowl. Add eggs and whisk to combine. Gently fold in brownie mix, flour and a pinch of salt.
Divide mixture between muffin tins and bake for 25-35 minutes, until cooked but still gooey in the middle.
Combine icing sugar with orange juice and drizzle over cooled brownies. You can add orange food colouring if you want to make it jaffa coloured.