Mix the cherries with 2 tablespoons of the caster sugar and the kirsch, if using, and leave for 2 hours to maximise their flavour.
Brush the inside of the baking dish with the melted butter. Sprinkle in the remaining 3 tablespoons of caster sugar and shake the dish so it coats the inside evenly.
Preheat the oven to 180°C/350°F/gas 4.
To make the batter, put the flour and salt in a mixing bowl and make a well in the centre. Add the eggs, egg yolk, sugar, lemon zest and the vanilla, if using. With a whisk, slowly incorporate the egg mixture into the flour until smooth.
Whisk in the milk and cream. In a small pan, heat the butter until it turns a pale hazelnut colour, then whisk it into the batter while still hot.
Mix the cherries and their juices into the batter and then pour into the baking dish.
Bake for 30–35 minutes, until the blade of a knife inserted into the mixture comes out completely clean.
Sprinkle a little caster sugar over and serve warm.
