Rhubarb & Custard Upside Down Cake

1. Preheat your oven to 180°C/Fan 160°C/Gas 4. Line a 20cm cast iron pan or round cake tin with baking paper.

2. Tip 75g caster sugar into a bowl. Finaly grate in the orange zest and use your fingertips to rub it into the sugar. Trim the rhubarb and slice into 2-3cm-long lengths. Add the rhubarb to the bowl of sugar and toss to coat the rhubarb. Arrange the rhubarb in the cast iron pan so it neatly covers the base. Shake over any sugar left in the bowl. Squeeze 2 tbsp orange juice over the rhubarb. Set aside while you make the cake batter.

3. Scoop the butter into a large mixing bowl and beat with electric beaters or a wooden spoon until soft and creamy. Add the remaining 175g sugar and beat into the sugar till soft and fluffy. Crack in 1 egg and add 1 tbsp of the self-raising flour. Beat into the butter. Repeat with the remaining eggs, adding 1 tbsp flour each time.

4. Sift in the remaining flour then add the custard powder and a pinch of salt. Pour in the soured cream. Use a flexible spatula to fold the wet and dry ingredients together. Scrape the cake batter into the pan, making sure it covers the rhubarb. Use a flexible spatule to level the top of the cake. Slide into the oven and bake for 40-45 mins till the cake is risen, golden and springy to the touch.

5. Take the cake out of the oven and let it sit in the pan for 1 hr. Place a large, flat plate over the pan. Protect your hands with oven gloves or tea towels, if necesary, and carefully flip over the pan so the cake slides out onto the plate. Peel off the baking paper. The cake is delicious served with cream or custard or can be eaten by itself. It will keep for up to 3 days in an airtight tin.