Cream the melted butter and 200g of Natvia for approx. 10 minutes.
Add the eggs, followed by the flour and lemon zest and beat together until well combined. Finally add the milk and beat until combined.
Grease and flour the bundt tin (or mini bundt tins) and fill with 1kg of cake mix (70g per mini).
Bake at 165C for about 45 minutes or until a skewer comes out clean.
For the soak
Heat the remaining 50g of Natvia and the juice of 2 lemons together until the Natvia has dissolved and the mix is simmering. Using a skewer, poke holes all over the cake and then brush the soak over the cake, allowing it to fill the holes made.