Heat oven to 180C/160C fan/gas 4.
Grease and line the base of a 23cm
square cake tin with baking parchment.
Butter the paper generously and sprinkle
with the demerara sugar. Halve the
plums and arrange in the base of the
tin in 1 layer, cut-sides down.
For the cake, melt the butter,
muscovado sugar and syrup in a large
pan over a low heat, stirring until smooth.
Cool for 10 mins, then stir in the eggs and
milk. Sift in the flour, bicarbonate of soda
and spices, then mix to a smooth batter.
Pour the batter into the tin, over the
plums, and bake for 45-55 mins until
firm to the touch. Cool in the tin for
10 mins, then turn out onto a wire rack
and leave to cool. Will keep in the fridge,
wrapped in baking parchment and foil,
for up to 5 days.