1) Place a rack in the lower third of the oven and preheat to 180C/Gas 4. Butter and flour the pan of your choice.
2) Sift the flour and salt into a medium bowl and set aside. Whisk the whole eggs, yolks, milk, and the vanilla together in a bowl, and set aside.
3) In a heavy duty mixer fitted with the paddle attachment, beat the butter at a medium speed until smooth, about 1 min. Gradually pour in the sugar, 50g at a time, to cream and lighten the butter. (This should take about 3 mins.) Once all the sugar is added, turn the machine off and scrape down the sides of the bowl and paddle with a rubber spatula. Continue to beat the butter mixture until light and fluffy, about 4 mins. Add the lemon zest and beat for 30 secs more. Turn the machine off and scrape the sides of the bowl again to assure even incorporation of the ingredients.
4) Turn the mixer to its lowest setting. Gradually pour in the flour, 35g at a time, and beat the batter for 30 secs. Gradually add the egg mixture. (It should take about a minute to pour all of it into the batter.) Remove the bowl from the mixer, scrape any batter off the paddle, and finish stirring the egg mixture into the batter with a rubber spatula. Take care not to over mix the batter, but make sure that you scrape the bottom of the bowl to evenly incorporate all of the ingredients.
5) Spoon the batter into the prepared pan and smooth over the top with a spatula. Put the cake in the oven and reduce the temperature to 160C/Gas 3. Bake until a toothpick inserted into the centre comes out clean, and the top springs back when lightly pressed, about 1 hr and 30 mins, for the tube or Bundt pans; and 50 mins to 1 hr for loaf pans.
6) Cool the cake, in the pan, on a rack, for 10 to 15 mins. Invert the cake onto a flat plate or cardboard. Re-invert the cake and set it right side up on the rack to cool completely. If not serving the same day, wrap in clingfilm and store at room temperature, for 4 to 5 days or freeze for 1 month.