Sift flour and salt into a bowl, Stir in sugar, then rub in butter until mixture resembles breadcrumbs. Blend egg and lemon zest. Press mixture into tin and prick pastry all over with a fork. Chill for 10 minutes.
Preheat oven to 375°F.
Bake pastry for 15 minutes, then remove from oven, leaving oven on.
Heat butter, honey and sugars in a saucepan until melted, then bring to a boil without stirring for 2 minutes. Remove saucepan from heat and stir in cream and nuts. pour over base, return tin to oven and bake for 25 minutes. Cool in tin.
Run a knife around pastry edge, invert on to a baking tray, place another tray on top and invert again. Cut into squares.