Source: BBC'S Good Food

6 ounces softened butter
6 ounces caster sugar or fine sugar
3 eggs
4 tablespoons milk
8 ounces self-rising flour
1 teaspoon baking powder
2 teaspoons ground cinnamon
6 tablespoons Nutella
2 ounces hazelnuts, roughly chopped

Preheat the oven to 185 degrees F. Grease and line the base of an 8-inch round cake pan.

Put butter, sugar, eggs, flour, baking powder, cinnamon and milk into a bowl. Beat with a wooden spoon for 2-3 minutes, or with an electric mixer for 1-2 minutes until light and fluffy. Tip 3/4 of the mix into the cake-pan, spread it level, then spoon the Nutella on in four dollops. Top with the remaining mix, swirl a few times with a skewer, then smooth to cover the Nutella. Sprinkle with the nuts. Bake for 1 hour to 1 hour 10 minutes, until risen, nicely browned and springs back when lightly pressed (cover with foil if it starts to brown too quickly). Cool in the pan for 10 minutes, then turn out, peel off the paper and cool on a wire rack. Wrap tightly in double-thick foil to keep fresh for up to a week.

This cake freezes well!