• Heat the oven to 160ºC fan and grease and line a 20cm cake tin.

To make the streusel

• in a medium bowl combine all the ingredients together. Using your fingertips rub them together until large chunks form. Set aside while you make the cake.

For the cake

• Put the flour, baking powder, salt, nutmeg, and sugar into a large bowl, Stir in the butter and eggs. Beat together for a minute or two until well combined.
• Stir in the apples until well distributed throughout the cake batter. Spoon half the batter into the cake tin. Sprinkle a few tablespoons of the streusel over then evenly spoon in the remaining batter. Evenly layer on the apple slices and sprinkle the top of the cake with the remaining streusel. Bake for 60-70 minutes until the cake is starting to pull away from the sides of the tin.
• Remove from the oven and leave to cool in the tin for 10 minutes before lifting out onto a wire rack to cool completely.

Make the glaze

• add the butter and maple syrup to a small saucepan until melted. Whisk in the powdered sugar and the sea salt until smooth. Drizzle the glaze over the cake and let set for 10 minutes before serving. Serve the cake slightly warm or at room temperature. Store in an airtight container in the fridge or freezer for up to 1 week.