First, whisk the egg yolks, flour, milk, vanilla, lemon zest and salt in a bowl - make sure it's large enough as you will add the whites in as well shortly. Once the mixture is smooth, set aside.
In a separate bowl, whisk the egg whites at medium speed until they form medium-firm peaks. Whisk in the sugar - it's often best to add part at a time - and whisk a little more until glossy. Then gently fold the whites into the flour-milk mixture, starting with a spoonful to loosen the mixture, then adding the rest. Take care to fold lightly so you don't lose all the air, but also you don't want streaks of white in there.
Heat the butter over a medium heat in a relatively small skillet/frying pan and swirl so the base has a thin coating. Add the pancake mixture and allow to cook approximately 5 minutes until gently brown on the underside.
Gently loosen the pancake from the skillet/frying pan with a spatula to make sure it is not stuck to the bottom and to ease spatula underneath. Use one or two spatulas to flip over the pancake. Don't worry if it doesn't work perfectly, as you are going to break it up soon anyway. And if it helps, you can first divide it into sections and flip each of them separately. Cook for another couple of minutes so the second side cooks and starts to brown.
Once the second side is starting to brown, gently dust with confectioner's/icing sugar and use two forks (or one large/two small spatulas if you are being careful with your skillet/pan) to break up the pancake into chunks. Allow it to cook a couple minutes more, turning pieces so the sugar gently caramelizes.
Remove from heat and dust with confectioner's/icing sugar as you serve it, with fruit compote on the side (see notes).