Gently mix together the cherries, sugar and kirsch and leave to macerate for two hours. (The sugar will slowly permeate the cherries and intensify their flavour.)
Preheat the oven to 180C/350F/Gas 4. Grease a baking dish with butter and sprinkle with sugar. Shake the sugar around the dish so that it is evenly coated, then tip out any excess.
For the batter, heat the butter in a small pan until it turns a pale hazelnut colour – this is called a beurre noisette. Do not allow the butter to burn or it will become bitter and carcinogenic. Remove the pan from the heat and set aside in a warm place.
In a large bowl whisk together the eggs, sugar and vanilla until creamy.
Add the flour, whisk until smooth, then slowly incorporate the milk, cream, salt and beurre noisette.
Mix the macerated cherries and their juice into the batter and pour into the prepared baking dish.
Bake in the oven for 30-35 minutes, or until the top is slightly domed and the blade of a knife inserted in the middle comes out clean.
To finish, sprinkle with caster sugar and serve warm.