I used to think a lemon was just a sour yellow fruit to add a touch of acidity to cooking. But there is more to it than that. There are cheap and useful everyday lemons, unwaxed lemons, organic lemons, Amalfi lemons and the charming Bergamot, which look like small, dumpy clementines.
The difference, and whether it is worth the extra expense and effort, depends on your recipe. Any involving grated lemon zest, the fine outer skin of the fruit where all the essential oils are stored, is more wisely made with a lemon that has seen no pesticides and waxes, be it a sorbet, old-fashioned mousse or vibrant sauce for pasta.
Most everyday lemons are coated with an edible wax to keep them longer and to make them shine on the supermarket shelf. No matter how safe the wax may be – and I am sure it is – I really don't want it in my posset or forming a scum on my G&T. I have read suggestions to scrub the fruit with soap and water before using. I'm not sure which is worse: a mouthful of bitter wax or the faint whiff of Ecover.
Unwaxed and organic lemons have a softness of colour that makes them look more like the fruit you see growing on the tree. They are twice the price, which means a considerable difference if you are using four in a lemon cake.
The beautiful Amalfi lemons, plump, leaf adorned and heady, are here, and will remain at their best until July. Expensive, fragrant and heavy in the hand, they are sweeter, brighter and more refined than the economy fruit. It is their fragrance that hooks me. I feel a temptation to pierce their skin with my thumbnail and inhale every time I walk past them in the kitchen. They smell more of their blossom than any of the fruit we know so well. Anyone who has seen the trees in bloom (buds, flowers and fruit all appear at the same time) lining the route along the Amalfi coast will know that smell and its spirited freshness. I like the subtle sourness they bring to my cooking – I often just squeeze them over spring greens or purple sprouting.
Yet even these babies are not my absolute favourite. It has been a treat this winter to get hold of the tiny, rare Bergamot lemon, with its dry, spicy notes. The fruits have a dry, sweet muskiness and darken to a glowing egg yolk yellow as they age. Infuriatingly difficult to get hold of, these are the lemons you need for making the Moroccan preserved lemons that perk up dark and mysterious tagines.
This week, I made a glorious lemon tart, softening the sourness with the zest and juice of a blood orange. And a big pan of soup, too, its depth flecked with shredded green and lemon zest, a taste of the season that will be upon us any day now.
SPRING GREENS AND LEMON SOUP
A lovely, fresh-tasting soup for a winter-spring day.
Leeks 3, medium
carrot 1, medium sized
celery 1 stick
vegetable stock 1 litre
bay leaves 2
spring greens 4 handfuls
lemon 1, small
Trim and wash the leeks, and slice them into thin rings. Melt the butter in a large saucepan and add the leeks, leaving them covered, to soften over a low heat. They should not colour.
Finely chop the carrot and celery and add to the pan. Pour in the vegetable stock, add the bay leaves, salt and pepper and leave to simmer for 20 minutes until the vegetables are soft but the colour is still bright.
Rinse the greens, place the leaves on top of one another and shred into thin ribbons.
Finely grate the lemon zest and add to the soup with the greens. Taste as you add, stopping when you feel it is sour enough. Simmer for 2 or 3 minutes until the greens are just tender. Check the seasoning, squeeze over the lemon juice and serve.
The tart case needs to be made with care, so the edges don't shrink as they cook, otherwise it will leak once the filling goes in. I keep a little bit of pastry aside for patching, so that if any cracks or gaps appear I can patch them before I add the lemon custard mix.
For the pastry:
plain flour 180g
caster sugar 1 tbsp
egg yolk 1, large
water a little
For the filling:
eggs 4. plus 1 extra egg yolk
caster sugar 250g
finely grated zest 2 unwaxed lemons
finely grated zest and juice 1 small blood orange
lemon juice 160ml
double cream 180ml
You also need a round 24cm tart case with a removal base and beans for baking blind.
Make the pastry by putting the flour into a food processor, adding the butter, cut into pieces, and blitzing to fine breadcrumbs. Or, rub the butter into the flour with your fingertips. Add the sugar and egg yolk and just enough water to bring to a firm dough. The less water the better – too much will cause your case to shrink as it bakes.
Tip the dough on to a floured board then roll to a little larger than your tart tin. Lift the pastry carefully into the tin, pushing into the corners, making certain there are no tears. Trim away any overhanging pastry, then put in the fridge for 20 minutes.
Set the oven at 200C/gas mark 6. Put a baking sheet in the oven to warm. Line the pastry case with kitchen foil and baking beans and slide on to the baking sheet. Bake for 20 minutes, then remove and carefully lift out the beans and foil. Return the pastry case to the oven for five minutes until the surface is dry to the touch. Remove from the oven and set aside. Turn the oven down to 160C/gas mark 3.
Make the filling by breaking the eggs into a bowl then adding the egg yolk and caster sugar. Grate the lemon and orange zest into the eggs. Pour in the lemon juice. Whisk until thoroughly mixed then stir in the cream. Pour the mixture into the baked tart shell and slide carefully into the oven. Bake for 35-45 minutes until the filling is lightly set. Ideally, the centre will still quiver when the tray is shaken gently.