To make the pesto, blend the nuts, basil, garlic and oil. Add the parmesan and pulse to mix.
Roll out the pastry into a long oblong shape.
Spread the mascarpone, then scatter over the tomatoes and cranberries evenly.
Carefully spread the pesto over the top, then roll up the pastry from the long edge into a swiss roll shape. Wrap in clingfilm and stick in the freezer for half an hour.
Preheat the oven to 200 degrees C. Slice the pastry roll into thin slices and place on a baking tray.
Loosely cover with foil and bake for 15 minutes. Remove the foil and bake for another 5 minutes until crisp.