- STEP 1
Preheat oven to 160 degrees Celsius (fan assisted) / Gas Mark 3; and grease an 9 inch (23 cm) spring form cake tin.
- STEP 2
Put pistachios into a food processor and blend to a fine powder.
- STEP 3
Melt butter gently in a pan and add to olive oil.
- STEP 4
Whisk eggs and sugar until light and fluffy.
- STEP 5
Slowly add the butter and oil mixture into the whisked egg mixture a little at a time with the whisk on a low speed until you have a thick emulsion.
- STEP 6
Sift the flour, then whisk the dry ingredients (polenta, plain flour, baking powder and pistachios) into the egg mixture.
- STEP 7
Add the juice and zest and fold into the mixture.
- STEP 8
Add the mixture into the prepared tin and bake in the middle of the oven for 50 minutes. Don't worry if the cake is slightly underdone in the middle - the cooling process will finish it off.
- STEP 9
Rest in tin for 10 minutes then turn out and cool on a cake rack.
- STEP 10
Dust with icing sugar then serve.