Preheat oven to 350°F. Grease a 9-inch springform pan with butter. Zest and juice ½ lemon and set aside.
In a bowl, cream together butter and sugar until light and fluffy.
Gradually beat in eggs.
Add salt, vanilla extract, lemon zest, and lemon juice.
Fold in ground almonds and baking powder. Mix until smooth.
Pour batter into prepared pan, smooth top, and bake for 35 minutes until golden brown. Remove from oven and let cool completely.
While the cake is cooling, prepare the cream. In a bowl, whip heavy cream until stiff peaks form. Zest and juice one lemon.
In a bowl, combine mascarpone cheese, lemon zest, lemon juice, and powdered sugar. Mix until smooth.
Gently fold whipped cream into mascarpone mixture. Spread evenly over the cooled cake.
Sprinkle lemon zest over cream and refrigerate until ready to serve.
