Preheat the oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
In a large bowl, cream together the butter and granulated sugar until light and fluffy.
Beat in the eggs, one at a time, then stir in the vanilla extract.
Gradually mix in the dry ingredients alternately with the milk until just blended.
Pour the batter into the prepared pans and bake for 25-30 minutes until a toothpick inserted into the center comes out clean.
Allow the cakes to cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.
In a mixing bowl, beat the mascarpone cheese and powdered sugar until smooth.
In another bowl, whip the heavy cream until stiff peaks form. Gently fold the whipped cream into the mascarpone mixture.
In a small bowl, combine the coffee liqueur and brewed espresso.
To assemble the cake, place one layer of cake on a serving platter. Brush the top with half of the coffee mixture.
Spread half of the mascarpone mixture over the cake layer.
Arrange a layer of ladyfinger cookies on top of the mascarpone mixture.
Repeat the layers with the second cake layer, remaining coffee mixture, mascarpone mixture, and ladyfinger cookies.
Dust the top of the cake with cocoa powder.
Refrigerate the tiramisu layer cake for at least 4 hours before serving.