Preheat the oven to 190°C (375°F/Gas 5) and lightly butter or oil a medium baking dish.
Peel, core and thickly slice the Bramley Apple; place the slices in a large bowl and toss with Caster Sugar and a little Lemon Juice until evenly coated, then spread the apple mixture in the prepared dish.
For the crumble topping, cut cold Unsalted Butter into small cubes and rub them into the Plain Flour with a pinch of Salt using your fingertips until the mixture resembles coarse breadcrumbs; stir in additional caster sugar to taste.
Evenly scatter the crumble mixture over the apples and gently press down in places so it sits snugly over the fruit.
Bake on the middle shelf for about 35–45 minutes, or until the topping is golden brown and the apple filling is bubbling at the edges.
Allow the crumble to rest for a few minutes before serving warm — delicious with custard, cream or vanilla ice cream if you like.
