Preheat oven to 170°C. Grease a 22cm (base measurement) cake pan and line the base with baking paper. Use an electric mixer to beat the butter, combined sugar, ginger, lemon rind and salt in a bowl until pale and creamy. Add eggs, 1 at a time, beating well after each addition. Add the flour, hazelnut or almond meal, buttermilk and baking powder. Beat until just combined. Add the grated apple. Stir to combine. Pour into the prepared pan and smooth the surface.

Use a mandolin or a sharp knife to thinly slice the extra apples. Arrange the apple slices, overlapping slightly, in a circle starting about 2cm from the edge of the pan and finishing in the centre. Brush apple slices with melted butter and sprinkle with extra sugar.

To make the hazelnut crumble, place the flour, sugar, butter and salt in a small bowl. Use your fingertips to rub the butter into the flour mixture until mixture resembles coarse breadcrumbs. Add hazelnut. Stir to combine. Sprinkle evenly around the edge of the cake.

Bake the cake for 55-60 mins or until golden brown and centre springs back when lightly pressed. Cool in the pan for 10 mins before transferring to a wire rack to cool completely.

Meanwhile, to make the burnt butter caramel, place the butter in a saucepan over high heat and cook, stirring occasionally, for 1-2 mins or until dark brown. Add sugar and stir to combine. Add cream, apple juice and salt. Stir to combine. Bring to the boil and cook for 4-5 mins or until the mixture thickens slightly. Set aside to cool.

Drizzle a little caramel over the apple crumble cake and dust with icing sugar. Serve with remaining caramel.