01 -
Set your oven to 175°C (350°F). Grease and flour a 9-inch round cake pan to prevent sticking.
02 -
In a medium bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.
03 -
In a large bowl, beat sugar, eggs, vegetable oil, and vanilla extract until smooth. Stir in the milk.
04 -
Gradually fold the dry ingredients into the wet mixture, stirring until just combined. Avoid overmixing.
05 -
Gently fold in the chopped rhubarb until evenly distributed.
06 -
In a small saucepan, whisk together milk, custard powder, and sugar over medium heat. Cook, stirring constantly, until the mixture thickens into a smooth custard.
07 -
Pour the cake batter into the prepared pan and smooth the top. Pour the custard over the batter and swirl gently with a spoon.
08 -
Place in the oven and bake for 35–40 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.
09 -
Allow the cake to cool for at least 15 minutes before slicing. Serve warm or at room temperature with whipped cream or ice cream.