Preheat the oven to 180ºC/350ºF/gas 4. Line a 12-hole muffin tray with paper cases.
Beat the margarine and sugar in a large bowl until pale and fluffy. Beat the egg in another bowl, then stir it into the margarine mixture. Sieve in the flour, baking powder and cinnamon, then fold through (don’t mix too much at this stage). Stir in the ground almonds.
Roughly chop the hazelnuts, then halve, core and chop the apple into rough 1cm chunks. Add the apple to the bowl along with half the hazelnuts and the vanilla extract, then stir briefly to combine.
Divide the mixture between the paper cases and sprinkle over the remaining hazelnuts. Place on the middle shelf of the hot oven for around 20 minutes, or until golden and an inserted skewer comes out clean. Leave to cool completely on a wire rack, then tuck in.