Preheat the oven to 180°C (approximately 350°F) convection.
Butter the bundt pan and sprinkle with breadcrumbs.
In the bowl of an electric mixer, beat the beat butter, sugar and vanilla sugar until light and fluffy. Add the eggs on at a time, beating well after each addition. Mix flour and baking powder in a bowl. Alternately add the flour mixture and the milk to the butter mixture, beginning and ending with the flour mixture until the batter is smooth (you may need to add a little more or less milk.) Beat in the lemon zest and limoncello. Scrape the batter into the pan and smooth the surface. Bake until a wooden pick inserted near the center comes out clean, 50-60 minutes. If the cake is over browning, tent it with foil. Cool in the pan, then run a metal spatula around the edges and center and invert the cake onto a plate. Serve