Put all but 12 blueberries into a small pan, squeeze in the juice from the lemon and add 50g Natvia.
Simmer over a low heat for a couple of minutes. Strain the juice and remove the blueberries. Return the juice to the pan and simmer for a few more minutes to make a thick syrup. Leave to cool.
Cream the butter with the lemon zest and remaining Natvia until light and fluffy.
Beat in the eggs, one at a time.
Sieve in the flour and baking powder and stir in.
Add the blueberries taken from the syrup and fold in.
Divide the mixture between 12 cupcakes cases and bake at 180℃ (350℉, Gas 4) for about 20 minutes when the cakes should be well risen and golden brown.
Cream the remaining butter with the Natvia icing until light and fluffy, then beat in the cream cheese and as much of the syrup as the mix will take without it becoming runny.
Spread the icing on top of the cakes and decorate with the reserved blueberries.
Adapted from Primrose Bakery Christmas by Martha SwiftIf you're not fussed about using sugar, just use golden caster sugar instead of the Natvia and golden icing sugar instead of the Natvia icing.Please note: calories and other nutritional information are per serving. They're approximate and will depend on exact ingredients used.