01 -
Preheat oven to 177°C. Grease two 20 cm round cake pans, line with parchment, and dust lightly with flour; tap out excess.
02 -
In a medium bowl, whisk flour, baking powder, baking soda, and salt. In a large bowl, cream butter and granulated sugar on medium speed for 3-4 minutes until pale and fluffy. Beat in vegetable oil, then add eggs one at a time. Mix in vanilla extract.
03 -
Add dry ingredients to butter mixture in three additions, alternating with milk. Begin and end with flour mixture. Mix only until just combined; do not overmix.
04 -
Divide batter evenly between prepared pans. Bake for 25-30 minutes or until a toothpick inserted in the center comes out clean. Cool cakes in pans on racks for 10 minutes, then remove and cool completely.
05 -
Combine flour and powdered sugar in a bowl. Cut in cold butter using a pastry cutter or fingertips until coarse crumbs form. Stir in lemon zest and vanilla. Spread crumbs on a parchment-lined baking sheet and bake at 177°C for 10-12 minutes until golden brown. Cool completely, then crumble into small pieces.
06 -
Whip cold heavy cream to stiff peaks in a chilled bowl. In a separate large bowl, beat mascarpone, sifted powdered sugar, lemon zest, lemon juice, and salt until smooth. Gently fold whipped cream into mascarpone mixture in three additions, maintaining a light texture.
07 -
Level cooled cake layers with a serrated knife if necessary. Place one cake layer on a serving plate. Spread one-third of lemon mascarpone cream evenly over the surface. Top with the second cake layer, pressing gently to adhere.
08 -
Frost top and sides of cake with remaining mascarpone cream, ensuring an even layer. Press cooled crumb topping over entire surface, covering top and sides.
09 -
Refrigerate cake for at least 60 minutes (preferably 2-3 hours) to allow the cream to set and flavors to meld. Slice with a sharp knife, wiping between cuts, and serve chilled.