Preheat oven to 180°C, top & bottom heat.
Toss apple slices with lemon juice and cinnamon powder.
Line muffin pan with cupcake liners.
In a bowl, combine all the ingredients for the crumble, and mash together with a fork until it resembles coarse breadcrumbs.Keep chilled until later.
In a large mixing bowl, mix flour, sugar, butter, eggs, and milk.
Mix until just combined.
Fill the liner about half way, then place apple rings on top of the batter.
Press it down slightly.
Then fill liners evenly with the rest of the batter.
Top with prepared crumble.
Bake for 35 minutes or until a skewer inserted in the center comes out clean.
Leave to cool in pan for 5 minutes.
Then remove muffins from pan to cool on wire rack.
Serve warm with ice cream or serve cold with hot coffee.