1. Preheat the oven to 220C (200C fan-forced) and place a large (26cm-28cm) cast iron skillet (or an ovenproof frying pan) in the middle rack of the oven to heat up.
2. Place the flour,castor sugar and salt in a medium bowl and use a whisk to combine. In a separate medium bowl,whisk together eggs,milk,vanilla,lemon zest and 1 tablespoon of the melted butter,then pour into the dry ingredients and whisk until combined. Do not mix too vigorously as the"pancake"will be tough.
3. Remove the hot skillet from the oven,drizzle in the remaining 2 tablespoons of melted butter and carefully swirl around the base of the pan. Return the pan to the oven for 20 seconds to recover the heat,then open the oven door,pull out the rack a little and carefully pour the batter into the hot skillet. Gently push the rack back in and immediately close the oven door. Bake for 18 to 20 minutes,resisting the temptation to open the oven door for the first 15 minutes as sudden loss in temperature can deflate the Dutch baby. It is ready when the sides are golden brown and puffy,and the middle is soft and pale yellow.
4. Remove from the oven and quickly transfer to a large plate and scatter with your topping of choice. Dust with icing sugar and serve immediately with a small bowl of yoghurt.
Serving suggestion:A squeeze of lemon and dusting of icing sugar would satisfy usually,but if you want to knock somebody's socks off,scatter with berries and lovely edible flowers.