Preheat oven to 220°C or 200°C fan. Lightly grease three 6-hole, 1/3-cup muffin pans.
Sift flour, baking powder, bicarbonate of soda, cayenne and ½teaspoon salt into a bowl. Stir in polenta, cheese, green onion and capsicum. Combine buttermilk, butter and egg in a jug. Gently fold buttermilk mixture into flour mixture until just combined. Don’t over-mix. Spoon into prepared pans and bake for 20 minutes, until golden. Turn out onto wire racks and leave to cool. Serve.