Preheat the oven to 180°C fan. Line a 12-hole muffin tray with cupcake cases.
Mix the flour, baking powder, cranberries, sweetener, and mixed spice together in a large bowl.
Beat the egg, melted spread, orange juice, orange zest and yoghurt together in a separate bowl.
Make a well in the centre of the dry ingredients, and pour in the liquid. Mix lightly until combined. Don't over mix or your muffins will be tough.
Spoon the mixture equally, between the cupcake cases.
Mix the mixed spice and granulated sweetener together and sprinkle over the top of the muffins.
Pop in the oven and bake for 15 minutes, until the muffins are risen and springy, and a skewer inserted into the middle comes out clean.
Allow to cool, then serve. These will keep for 3-4 days in an airtight tin.