Before you make the curd, zest the 1 orange and 2 lemons and set aside (it's easier to zest a whole fruit than one that's been juiced!)
To make the curd put the juice from the orange and lemons into a saucepan with the sugar and cornflour. Whisk over a gentle heat until it starts to thicken then turn off the heat and whisk in the butter.
Transfer to a bowl to cool while you make the cake
Preheat your oven to 180 Fan / 200 C / 400 F / Gas 6. Line a 10 inch (25cm) square baking tin or dish with parchment
Whisk together the yoghurt, milk, oil and vinegar
In a large bowl put the flour, baking soda, zest and sugar and mix together
Add the milk mixture and still together until well incorporated then pour into the prepared tin
Drop spoonfuls of roughly half the curd all over the top of the cake then use something pointed to ripple the curd through the batter
Bake for 30-35 minutes until the cake is cooked in the centre. To test if the cake is cooked, insert a cocktail stick in the middle of the cake - if it comes out clean with no raw batter clinging to it the cake is cooked. If not, return the cake to the oven to cook for a few more minutes and repeat the process
Allow the cake to cool for 10-15 minutes in the dish before turning out onto a wire rack to cool completely
Serve with a spoonful of the extra curd on top
Notes
Store any cooled leftovers in an airtight container at room temperature
You can also freeze this cake - portion and wrap in foil or put into freezer container
Recipe by The Cook & Him at https://thecookandhim.com/recipes/st-clements-curd-cake/