Heat the oven to 160°C/gas 3. Generously butter a 24cm push-up-bottom cake tin.

Place the flour in a bowl, add the butter, sugar, orange zest and egg yolks, and work together with your fingers until all the ingredients are evenly blended - the mixture will be quite sticky. Put the mixture into the prepared cake tin and spread it out with your hands.

Make a pattern in the top of the cake mixture with a knife or pastry cutter, and brush the surface with a little milk. Bake for 35 minutes, until the cake is golden brown and has come away from the sides of the tin.

Leave to cool in the tin for 5 minutes before turning out.