Begin by making the cupcakes. Place the cupcake liners in the cupcake pan and set it aside. Preheat the oven to 350 degrees Fahrenheit, and mix together all of the dry ingredients EXCEPT the sugar in a small bowl, except the poppy seeds. Set it aside. In another small bowl, mix together the sour cream, milk, vanilla extract, and lemon juice, and set that bowl aside as well. In a large bowl, cream together the butter and the sugar, then add the eggs, one at a time, mixing well between additions. Add the grated lemon zest and then alternate between adding the flour mixture and the lemon juice mixture until they're all completely combined. Stir in the poppy seeds. Evenly distribute the batter between the cupcake liners. Place the cupcake pan in the oven and bake for 30-35 minutes or until a toothpick inserted into the cupcakes comes out clean.