A simple cake that makes the most of rhubarb's tart flavour - so enjoy it while it is in season!
Preheat oven to 170c, line a 2lb loaf tin and have all your ingredients at room temperature.
Prep the rhubarb. Wash stalks, trim them so they are no longer than the loaf tin then cut in half and pat dry. In a large frying pan / saute pan heat 1tbsp caster sugar and half of the orange juice over a low heat. Add the rhubarb, cover with the sugar, and heat on low for approx 5 minutes until it is soft. Watch it doesn't burn - add more juice if needed - or a splash of water. Remove from heat and put to one side.
In a stand mixer or with a hand mixer, cream the sugars and butter/stork together until soft and fluffy. With butter it will take several minutes, with a Stork-type spread, just a couple of minutes.
Slowly add the eggs, buttermilk and zest.
Add the flour and baking powder, and mix gently until just combined.
Spoon into the prepared loaf tin and smooth the top. Place slices of the rhubarb gently on top and press in gently - just enough for it to stick to the mix.
Put immediately into the oven (hang around and the rhubarb will sink during cooking). Cook for approx 50 minutes until a toothpick or cake tester comes out clean.
Squeeze the remaining orange juice over the top when it comes out of the oven. Transfer to a rack and allow to cool.
Store in an airtight tin or tightly wrapped in baking paper / foil.
The amount of rhubarb you will need will depend on how thick your stalks are. If they are really skinny, don't half them. Better to cook too many - you can use the leftovers to serve with the cake or enjoy with some Greek yoghurt.