• Preheat oven to 375F. Line the cupcake tin with paper liners.
• Add the sugar and lemon zest to the bowl of a food processor then pulse until zest is broken up and the sugar is pale yellow In color.
• Whisk the flour, baking soda, baking powder and salt into a large bowl then whisk together and set aside.
• Add the eggs, milk, melted butter, vanilla, sour cream, and sugar to a medium bowl and whisk together.
• Add the wet to the dry mixture and mix until just combined. Stir in the poppy seeds and lemon juice. Fill cupcake papers about 3/4 the way up. Bake for 5 min at 375F then reduce temperature to 350F and bake another 10-12 or until the springy to the touch.
• Frost the cupcakes with the buttercream. (The frosted cupcakes can be refrigerated in an airtight container for up to 3 days; bring to room temperature before finishing.)

For the buttercream

• With a mixer, cream the butter and zest together. Add the powdered sugar ½ cup at a time.
• Add in your vanilla extract, heavy cream, lemon juice. The frosting may curdle at this point, but keep mixing it will smooth it out.
• Mix on medium-high for about 8 minutes until light and fluffy. Frost your cupcakes with a spatula or piping bag fit with a star tip. Top with a few additional poppy seeds.