Preheat your oven to 325 degrees F. Line 16 standard muffin cups with papers.
Sift flour, baking powder and baking soda into a medium bowl. Add half of the sugar and all of the salt and whisk to blend evenly.
In a small bowl, whisk together eggs, yolk, oil, remaining ½ cup of sugar, melted butter and lemon zest and vanilla until frothy. Add half of the flour mixture whisk gently. Whisk in half of the milk. Whisk in remaining flour followed by the rest of the milk. Do not over-mix.
Spoon the batter into the lined muffin cups and divide it evenly. Bake for 18-22 minutes until a cake tester comes out clean. Transfer pan to a rack to cool 5 minutes. Remove cupcakes from the pan and let cool completely on a rack.
Make the frosting. Beat soft cream cheese until smooth. Add 2 tablespoons of cream and beat until very smooth and there are no lumps. Then gradually add remaining cream and beat until it forms soft peaks. Gradually beat in sugar until it is thickened to a spreadable consistency, then mix in lemon juice.