Preheat the oven to 180°C/gas mark 4. Grease a 20 x 30cm baking tin and line with baking parchment.
Combine the butter and chocolate in a bowl set over a saucepan of simmering water and stir continuously until melted, making sure the bowl doesn't touch the water. Cool, then stir in 225g caster sugar. Beat in 3 eggs, one by one, then mix in the flour and set aside.
In a separate bowl, whisk the soft cheese with the remaining 50g caster sugar and 2 eggs, until creamy. Drop alternate spoonfuls of each mixture into the prepared baking tin. Using a spoon, swirl together to create a marbled effect. Scatter the cherries on top and bake for 30-35 minutes. Place on a wire rack, cover with foil and allow to cool before serving.