01 -
Toss unsalted butter, granulated sugar, and whipping cream into a heavy saucepan. Heat it up until it hits a gentle boil, stirring now and then. Let it bubble for about a minute, always stirring so nothing sticks. Take it off the heat and let it cool a bit.
02 -
Spread out your batter in a buttered 23 x 33 cm pan, smoothing things flat with a spatula. Slide it into the oven for 45 minutes or so. Test with a toothpick—if it pops out clean, you're set. Once baked, pull it out and give it a little time to cool.
03 -
Pour in the melted butter, milk, and chopped rhubarb with your dry mix. Stir gently, just enough so it's all mixed, but don't go wild—overmixing will mess up the texture.
04 -
Turn on the oven to 175°C first. Grab a big bowl and mix up the flour, sugar, baking powder, and salt really well.
05 -
Slice up the cake while it's still warm and pour on that yummy butter sauce. Warm up the sauce a bit before serving if you like.