Grease and line with baking paper three 20cm (8 inch) round springform baking pans.
In a large bowl, add white sugar, plain flour, corn flour, baking powder, bicarb soda, salt, poppy seeds and ground cardamom. using a wooden spoon, mix until combined. Note: you won’t need electric beaters for the cake.
In a separate bowl, add eggs, buttermilk, canola oil, vanilla extract and lemon zest. Whisk together until fully combined.
While stirring with the wooden spoon, slowly add the buttermilk mixture to the flour mixture and continue stirring until combined.
Add hot water and stir until fully combined.
Pour the cake batter evenly into the 3 baking pans. I find this step easiest by weighing the mixture, bowls and baking pans and using these measurements to evenly spread the mixture across the baking pans.
Place in oven and cook for about 25 minutes or until a skewer inserted into the centre of the cake comes out clean.
Remove from oven and allow to cool in baking pan for 10 minutes before removing from pan & inverting cake onto a wire rack to cool completely.
Lemon Curd Filling
Combine caster sugar, corn flour, lemon juice, lemon zest and water in a small saucepan over medium heat. Stir to combine
Cook for a few minutes while stirring regularly, until mixture comes to a boil and thickens.
Reduce heat to low and continue heating for about 30 seconds until mixture is very thick.
Remove from heat and add egg yolks and butter. Stir until butter is melted and all ingredients are fully combined. Set aside to cool, then place in refrigerator to chill and thicken.
In a large mixing bowl, add egg whites & pinch of salt and beat with an electric mixer until soft peaks form.
Add vanilla extract and mix to combine.
Gradually add caster sugar, beating well after each addition until mixture is thick and glossy.
Place first cake on a plate and place half the lemon curd mixture on top and spread to cover the cake.
Place the second cake on top and add the remaining lemon curd mixture on top and spread to cover the cake.
Place the third cake on top and add meringue icing to the top and sides of the cake.
Using a kitchen torch, toast the meringue icing to the desired result. Be careful using the torch to avoid burning the meringue. Do not hold the flame in the same place for more than a couple of seconds. A sweeping motion works best.