In a heavy bottom pan, melt the butter
Add the sugar, port and lemon juice
Over medium flame cook to a caramel
Arrange the plums in the caramel cut side up, filling the pan
Cut the puff pastry to fit the pan (circle) and lay on the top of the plums
The easiest method for doing this is to lay the puff pastry on the hot pan, roll a rolling pin over it and pull away the excess
Bake in a 400 degree oven for 20 -25 minutes till puff pastry if browned
While still hot place a plate on the pan and flip the tarte out
Serve with whip cream