Preheat the oven on bake at 160c or 320F and lightly grease and line a cake tin.

In a jug mix together the butter and avocado oil.

In a separate bowl mix whisk the eggs with the sugar until light and creamy and then combine the oil and egg mixture.

Add the dry ingredients, juices and zest and mix well.

Pour into the waiting cake tin and bake in the oven for 45-60 minutes until the cake is golden on top and when pressed gently, springs back.

Cool the cake in the tin for 10 minutes before turning out on to a wire rack and cooling further.

Serve with fresh berries and cream or store in an airtight container when completely cold for up to 3 days.