When I hosted my book group here last month I decided to make a chicken tagine to serve the girls, but lacking a supply of preserved lemons, I had to improvise. It's possible to substitute sliced fresh lemons – I've done it – but the result just isn't the same. Here's my ad hoc remedy.
Select 2 lemons with nice shiny skins and scrub them clean with a paste of warm water and baking soda. This is a trick my brother's wife hipped me to years ago – nothing fancy, just dump a spoonful of baking soda in your hand, add a little water, and use both hands and a little firm pressure to scour the fruit all over, then give them a thorough rinsing. I do this whenever I'll be using the peel of any citrus (even when it's organic) – for marmalade, candied peel, whole preserved fruit.
(The French have a great little word for kitchen tricks like this: a 'truc' is any little thingie or whatsit or trick. We all have them, and sometimes they can be a revelation to others. I'm happy to share mine, and just added 'Truc' as a category. More to follow.)
Slice the lemons thinly, a little less than an eighth of an inch thick (make sure your knife is wickedly sharp).
Prick out the seeds and arrange the slices in a single layer on a flat plate. Sprinkle with about 2 teaspoons of kosher salt and half a teaspoon of sugar. (Sugar isn't generally used for long-preserved lemons, but I thought it might help with mellowing them on a tight schedule.) Add another layer of sliced lemons, then sprinkle with more salt and sugar.
Once all the slices have been arranged and sprinkled, place another plate on top, weight it, and leave to stand at room temperature for about 3 hours. Mine didn't give up enough liquid to run over, but if that's a concern, you can put the whole thing in the sink.
Before using, give them a quick cold-water rinse and drain them (or pat them lightly with a paper towel). Slice, dice, or quarter them to use in your recipe.
Duly chastened for my failure to have any of the 'real' thing on hand, I will now set about packing a jar full for future use.