Cream together soften butter and sugar till pale and sugar is dissolved
Stir in eggs one at a time then add vanilla
Sift in dry ingredients, just till combined
Pour in milk and stir
Fold in blueberries and lemon zest
Line a muffin pan with baking cups and scoop spoonfuls of batter into wells. Sprinkle the tops with sugar if desired and bake at 350ยบ for 30 mins just till edges are golden brown