Lemon Poppy Seed Cake

Ingredients

• 3 cups cake flour
• 1 ¾ cups sugar
• 4 ½ tsp baking powder
• ½ tsp salt
• 2-3 tbsp poppy seeds
• 2 sticks unsalted butter, softened and cut into 1-inch cubes
• zest of 1 large lemon
• 1 ¼ cups buttermilk
• 5 egg whites
• ½ tsp. vanilla
• 4 oz. mascarpone or cream cheese, cold
• 2½ tbsp. unsalted butter, at room temperature
• 1¼ cups powdered sugar
• 2 tsp. lemon extract
• zest of ½ a lemon
• 1 cup heavy cream, chilled
• 2 sticks unsalted butter, softened
• 8 oz cream cheese, softened
• 6-8 cups powdered sugar
• zest of 1 lemon
• fresh lemon juice, to taste
• 1 tsp. vanilla extract