Rhubarb and pink grapefruit jam

Makes enough for four 250g/8oz jam jars

This jam is delicious in a Bakewell tart or with toasted sourdough and salty butter (Lisa Barber)

This jam is citrussy and sharp – delicious in a Bakewell tart or with toasted sourdough and salty butter for breakfast.

1kg/2lb rhubarb
3 pink grapefruit
1kg/2lb caster sugar

Wash and pat dry the rhubarb. Cut roughly into 2cm lengths. Peel the zest from the pink grapefruit (easiest with a potato peeler) and chop finely. Now slice the grapefruit itself into halves and squeeze out the juice. Put the chopped rhubarb, grapefruit zest and juice into a heavy bottomed stainless-steel pan. Pour in the caster sugar, combine and allow to macerate for 20 minutes. Next, place over a high heat and bring to a vigorous boil.

Keep the heat high – the jam should bubble thickly. Stir frequently to prevent it from catching and burning on the base of the pan. Splash off any foam from the surface.

The best way to check whether a jam has set is to place an empty plate in the fridge and leave it there to chill for about 20 minutes. When it's cold, remove it and place small spoonfuls of jam on it. This allows the jam to cool quickly so you can check its consistency. Ideally, it should be runny but not too thick as to be cloying. For this jam, 20 minutes' cooking time should be sufficient.

Spoon the jam into four sterilised jam jars and leave to cool completely. Then put in the fridge until ready to use.