In a large bowl, mix together butter and sugar. Beat until creamy. Add in eggs, vanilla, lemon extract and sour cream and mix together until combined.
In a separate bowl, mix together flour, baking soda, baking powder and salt. Slowly add dry ingredients to the wet ingredients. Mix just until combined.
Split dough in two and place in saran wrap. Refrigerate dough for 1-2 hours.
Once dough has chilled, preheat oven to 350°F. Roll out dough on a baker's mat or parchment paper to about 1/4" thick. Add up to another 1/4 cup flour if dough is still sticky. Cut with floured cookie cutter.
Bake for 8-9 minutes, until edges are slightly golden. Then allow to cool on pan for 2 minutes and then transfer to a cooling rack.
For the Frosting:
For both the buttercream, combine all listed ingredients in a medium-sized bowl. Feel free to add in food coloring. Mix with an electric mixer until smooth.