Prepare the Sponge Cake:

• Preheat oven to 350°F.
• Grease and line an 8-inch round cake pan with parchment paper.
• In a bowl, whisk together flour, baking powder, and salt.
• In a separate bowl, cream butter and sugar until light and fluffy.
• Add eggs one at a time, beating well after each addition.
• Mix in vanilla extract.
• Alternately add dry ingredients and milk, beginning and ending with dry ingredients.
• Pour batter into prepared pan and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
• Let cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.

Prepare the Lemon Cream Filling:

• Whip heavy cream to stiff peaks; set aside.
• In another bowl, mix mascarpone cheese, powdered sugar, lemon zest, and lemon juice until smooth.
• Gently fold whipped cream into the mascarpone mixture until well combined.
• Refrigerate until ready to use.

Prepare the Crumb Topping:

• Preheat oven to 350°F.
• Spread flour on a baking sheet and bake for 5 minutes to remove the raw taste; let cool.
• In a bowl, mix cooled flour, sugar, melted butter, and lemon zest until crumbly.

Assemble the Cake:

• Once the cake is completely cooled, slice it horizontally to create two layers.
• Place the bottom layer on a serving plate and spread the lemon cream filling evenly over it.
• Place the top layer over the filling.
• Gently press crumb topping onto the top and sides of the cake.
• Dust with powdered sugar before serving.