Preheat oven to 200°C (180°C for fan assisted ovens)/Gas Mark 6.
Unroll the pastry onto a lightly floured work surface. Brush the fluted tart tin with melted butter and line with the pastry by pushing the pastry in at the edges and gently pricking the base. Trim the pastry using the rolling pin. Sprinkle the base with ground almonds.
Place plums into a bowl and toss with the caster sugar. Tip in to the tart tin and add the chopped stem ginger. Put in the oven to bake for 25 minutes.
Sprinkle with almonds and return to oven for 5 minutes then allow to cool in the tin on a wire rack.