For the madeleines: Beat the sugar with the eggs until pale and frothy. Put the flour and baking powder into a separate bowl and add the lemon zest. Mix the honey and milk with the cooled butter, and then add to the eggs. In two batches, fold in the flour mixture. Cover and leave to rest in the fridge for a few hours, or overnight.
For the lemon curd: Meanwhile, put the butter, sugar, salt and lemon zest and juice into a small saucepan and heat gently until the sugar and butter have melted. Remove from the heat. Whisk the egg yolks in a bowl, and then add to the pan and whisk vigorously. Return the pan to a low heat and whisk constantly as the curd starts to thicken. Do not stop whisking or the eggs will curdle (if the curd starts to boil, take off the heat). Once the curd thickens and releases a bubble or two, remove from the heat and pass the curd through a sieve into a bowl. Place cling film in direct contact with the curd and refrigerate for at least an hour, preferably overnight.
Preheat the oven to 375 degrees F/190 degrees C /Gas 5. Butter and flour a 12-shell madeleine tin. Put the lemon curd into a piping bag fitted with a small, pointed nozzle and place in the fridge. Put a heaped tablespoon of batter into each madeleine shell and press a raspberry deep into the batter. Bake for 5 minutes and turn the oven off for 1 minute (the madeleines will get their signature peaks), and then turn the oven on to 325F/160 degrees C/Gas 3 and bake for a further 5 minutes. Transfer the madeleines to a wire rack and leave for a few minutes until cool enough to handle. Repeat with the remaining batter and raspberries. While the second batch is baking, pop the piping nozzle into the mound in each baked madeleine and squirt in a teaspoon's worth of lemon curd. Repeat with the second batch. Dust with icing sugar and serve straightaway.