Preheat your oven to 160°C. Using a pastry brush, brush melted butter into every crevice of your train cake pan. Dust generously with flour. Tip over and tap to remove excess flour. Set aside.
In a large bowl, add your caster sugar and lemon zest. Rub the lemon zest into the sugar between your fingers until the lemon zest is thoroughly coated.
Add flour, baking powder, baking soda and salt. Whisk and set aside.
In a separate bowl, combine melted butter, sour cream, eggs and vanilla. Beat (preferably using an electric mixer with the beater blade; do not use a hand whisk. If mixing by hand, use a wooden spoon) until well combined.
Sift in your flour and sugar mixture and beat on a medium speed until just combined (1 minute maximum). Be cautious of over-mixing your batter.
Spoon into your greased train cake tin until each section is approximately 3/4 full. Flatten the mixture and ease it into the sides rather than the middle. Tap the tin on a surface to remove air bubbles.
Bake in a preheated oven for 17-25 minutes until a toothpick inserted into the centre comes out clean.
Once baked, place a wire rack on top of the tin (the cake should be touching the wire wrack. Flip both the tin and the wire rack so that the rack is now at the bottom with the tin inverted on top. The flat base of the train cars should be resting against the wire wrack.
Leave to cool for 10 minutes. Once cooled slightly, lift the cake pan a little and shake gently to ease the cakes onto the rack. You may need a toothpick to loosen the edges at the top of the cakes. Leave to cool completely on the wire wrack.
