For the sponge, preheat the oven to 180C/170C Fan/Gas 4. Grease a 900g/2lb loaf tin with butter and line with baking parchment.
In a large mixing bowl, cream the butter and sugar together until pale and fluffy. Beat in each egg with a heaped tablespoon of flour until all the eggs are combined (this will prevent the mixture from curdling).
Stir in the rosewater, lemon zest and lemon extract. Fold in the remaining flour and ground pistachios. Pour the mixture into the prepared tin and bake for 45 minutes. Check after 35 minutes, if the cake is browning too quickly, cover the top with aluminium foil.
While the cake is cooking prepare the rose glaze. Add the apple juice, honey and rosewater to a small saucepan and heat gently until combined. Add the apple slices and poach for 10 minutes, or until softened.
Line a tray with non-stick paper. Using a slotted spoon, place the apple on the prepared tray to cool. Once cool enough to handle, arrange the slices in three rows, with each slice facing the same direction and the thin ends overlapping.
When the cake is cooked, reheat the remaining syrup to 115C on a sugar thermometer (if you don’t have a thermometer, bring it to the boil and simmer for 5 minutes until syrupy). Using a skewer, poke holes into the top of the cake and pour the syrup over.
Roll up a row of apple slices tightly into a rose shape and place on top of the cake (you may need to make a small hole to support it). Repeat with the remaining 2 rows.
For the candied lemon peel, slice the lemon rind into strips and place in a pan of boiling water for a few minutes. Drain, discard the water and clean the pan. Add fresh water to the pan, bring to the boil and return the lemon peel. Repeat this process a total of 3 times (this will remove any bitterness from the peel).
Make a sugar syrup by mixing the sugar with 100ml/3½fl oz water in a pan. Heat gently until the sugar is dissolved, then bring to a simmer and poach the lemon peel for about 5 minutes, or until it is translucent. Remove from the heat and set aside to cool.
Once cool, remove the lemon peel and arrange over the top of the cake. Finally, sprinkle some of the dried rose petals over the cake.