To stop the custard or jam seeping to the edge of the batter and possibly burning during baking I came up with a method to make channels in the batter and spoon the fillings into it. Use a spoon or knife to make a channel like this:
Take care to spoon the custard and jam into the channel, making sure there is batter protecting it from the edges of the tin:
You get a lovely big slice from a bundt cake like this; the batter was the perfect quantity to fill the tin and, when baked, the cake only needed a thin trim to cut off the crust and make it stand nicely on a plate.
The sponge is lovely – soft and springy, and would be nice on its own with a buttercream or full covering of icing. Definitely a keeper!
2 tablespoons custard powder
1 tablespoon caster sugar
225g unsalted butter, at room temperature
450g caster sugar
2 tbsp vanilla extract
350g plain flour
1/2 tsp bicarbonate of soda
250ml natural/Greek style yogurt
4-5 teaspoons jam – I used strawberry
150g icing sugar
2-3 tablespoons warm water