01 -
Set your oven to 350°F (175°C) and butter a 9-inch square baking dish.
02 -
Grab a medium bowl and mix the flour, baking powder, and salt together.
03 -
In a big bowl, beat the sugar and soft butter until fluffy. Add the egg and vanilla and mix well.
04 -
Add the flour mix and milk bit by bit, starting and ending with flour. Stir in the chopped rhubarb last.
05 -
Dump the mix into your buttered pan and smooth it out. Let it bake for 45-50 minutes until a stick comes out clean when poked in the middle.
06 -
Put butter, sugar, and thick cream in a pot over medium heat. Keep stirring until everything melts together smoothly. Turn off heat and add vanilla.
07 -
Pour some warm sauce over each slice of cake before eating.