Preheat the oven to 180ºC/Fan 160ºC/Gas Mark 4. Grease the base and sides of a 900g/2lb loaf tin, then line with non-stick baking parchment.
Sift the flour, baking powder and caster sugar into a bowl. Beat TheLake District Dairy Co. LemonQuark, egg yolks, lemon zest and oil together in a jug. Use an electric whisk to whisk the egg whites together in a clean bowl until they form soft peaks.