1. To make the custard, place custard powder in a jug, add a tablespoon of the milk or so to the powder and mix.

2. Add the rest of the milk and sugar to a saucepan and heat over a medium heat until warm but not boiling, stirring all the time.

3. Pour the milk into the custard powder paste and stir continuously so it doesn't go lumpy, return to the saucepan and place back on a medium heat, still continuously stirring, the mix with thicken, this will take 5-10 minutes. Keep stirring otherwise it will go lumpy. Once thick, remove from the heat and pour into a jug or bowl, cover with cling film and allow to go cold.

4. Grease and line a 8 inch cake tin, sprinkle 1tbsp sugar over the bottom of the tin, cut the rhubarb into pieces that will go all the way across the tin and lay them in the bottom.

5. Place all the other ingredients for the cake in a bowl and with an electric whisk, whisk until you get a nice smooth cake batter.

6. Pour the cake batter over the rhubarb, place the cake in an oven preheated to gas mark 4 and bake for 1 hour.

7. Once cooked through (a skewer pushed into the middle should come out clean) remove from the oven and leave in the tin for 10 mins before turning out.

8. Turn out onto a cake rack and allow to go cold, what was the bottom in the tin is now going to be the top.

9. Once both the cake and custard are cold, spread the custard over the top of the cake.