Preheat oven to 350˚F with a rack in the center of the oven. Butter the sides and base of two 9" cake pans and line the bottom of each pan with a ring parchment paper.

In a large mixing bowl with an electric hand mixer, cream together 12 Tbsp softened butter and 1 cup sugar for 2 minutes on high speed. Add eggs one at a time mixing just until incorporated.

In a small bowl, whisk together 2 cups flour, 2 1/2 tsp baking powder and 2 Tbsp poppy seeds. Add half of the flour mixture, mixing just until incorporated.

Bake at 350˚F for 20-23 minutes or until a toothpick inserted into the center comes out clean. Let cake cook in pans 10 minutes then transfer to wire racks, remove backing and and cool to room temperature.

Sprinkle the edges of the cake with poppy seeds if desired. Pipe remaining 1/3 of the frosting as desired over the top and place a slice of fresh lemon over each puff of frosting.

In a large mixing bowl with an electric hand mixer, beat 1 cup butter on high speed until smooth and creamy (2 min). Add 4 oz softened cream cheese and beat until completely smooth. Add 4 cups powdered sugar, 3 Tbsp lemon juice and 1 tsp vanilla and beat on high speed until whipped and fluffy (5 min).