Preheat the oven to 210C/410F. Place butter into a 10 inch skillet over a low heat. Once the butter has melted, use a pastry brush to brush the butter all over the bottom and sides of the skillet.
Place flour, zest, sugar, salt, lemon juice, eggs and milk into a blender and blitz until smooth. Alternatively, you can place the dry ingredients into a bowl and the wet into a jug. Lightly whisk the dry and beat the wet, then gradually add the wet ingredients into the dry, whisking as you go until you have a smooth mixture.
Tip the mixture into your prepared skillet, there will be a ring of butter around the edge, that's fine.
Place in the oven for 12-15 minutes, until golden all over, risen and puffy. It will be slightly darker around the edges and will sink as it cools.
Once cool, place double cream and icing sugar into a medium sized bowl and whisk until it reaches soft peak stage; you want it to hold its shape, but be soft and light too!
Spoon the cream into the centre of the pancake, then sprinkle blueberries all over and garnish with quartered lemon slices. Dust with icing sugar and serve.
Lemon and Blueberry Dutch Baby Pancake is best eaten on the same day, but will keep covered in the fridge for 2 days without the cream. Remove it from the skillet and place on a plate for storage. Bring to room temperature before serving.