01 - Preheat oven to 350°F. Grease and flour two 8-inch round cake pans.
02 - Beat butter and granulated sugar together until light and fluffy. Add eggs one at a time, beating well after each addition.
03 - Mix in lemon zest, lemon juice, and vanilla extract until incorporated.
04 - Whisk together flour, baking powder, and salt in a separate bowl.
05 - Add dry ingredients to wet mixture in three parts, alternating with milk. Begin and end with flour. Mix until just combined.
06 - Divide batter evenly between prepared pans. Smooth the tops.
07 - Bake for 25 to 30 minutes or until a toothpick inserted in the center comes out clean.
08 - Let cakes cool in pans for 10 minutes, then turn out onto wire racks to cool completely.
09 - Beat mascarpone and powdered sugar until smooth. Add lemon juice, lemon zest, and vanilla.
10 - Whip cream in a separate bowl to stiff peaks.
11 - Gently fold whipped cream into mascarpone mixture until fully combined.
12 - Place one cake layer on a serving plate. Spread with half the lemon cream. Top with second cake layer and spread remaining cream on top and sides.
13 - Chill cake for at least 1 hour before serving. Dust with powdered sugar and garnish with lemon slices or zest.