By Annabel Langbein

Whenever you taste a dish and think it tastes a bit flat or dull, chances are it's either salt or acid that's missing.

Think about it - a spoonful of tangy yoghurt over Moroccan kebabs, a squeeze of lemon juice over a crispy fish fillet, creme fraiche dolloped over a wedge of apple tart, black vinegar on a shanghai dumpling, lime over a taco, a teaspoon or two of sherry vinegar in a rich beef stew, or rice vinegar tossed through sushi rice - it's the acid that gives each of these dishes a zing that is so pleasing on the palate.

Every culture has its own repertoire of preferred acids, be they wine, beer, verjuice, cider, tamarind, cultured dairy foods, such as yoghurt and buttermilk, tangy cheeses, citrus and a world of different vinegars. Tangy fruits, such as pineapple and passionfruit, also deliver acid tones, as do tomatoes and pickles.

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Out of this vast repertoire of acid flavours, lemons are probably the one ingredient I couldn't cook without. It's not just the clean, bright jolt of freshness that their juice delivers, but also their fragrant zest, which imparts an appealing depth and tone to dishes both sweet and savoury, a taste that is less about acid and more about giving a dish a layered depth.

To retain the bright freshness of lemon juice, always add it at the last minute, rather than while a dish is cooking. When it comes to grating the zest, using a microplane ensures you don't cut into the bitter pith that sits just under the skin. Don't be tempted to grate a whole lot of zest for later use, as the volatile oils will disappear into the air.

I'll often put lemon zest into a pesto, but not the juice, so that it will stay fresh and green. Lemon juice, along with other acids, takes the verdant colour out of green vegetables and herbs and quickly turns them a dull, sad brown. On the other hand, the colour of red vegetables is enhanced by acid, so dishes made with beetroot, red cabbage or tomatoes become more vivid with its addition.

Lemon pith can be bitter, especially in varieties other than wildly juicy Meyer lemon. The Meyer is my favourite lemon variety - its acidity is gentler than other lemons, and it's a softer fruit that's easier to squeeze.

Clever Mother Nature delivers these versatile fruits during the winter months, exactly when we need their burst of vitamin C in our diets, so now is the time to stir the juice into a lemon and honey drink to ward off winter ills.

Come midsummer, lemons will be hard to find, and we will have to rely on sprayed and waxed imports. Luckily, lemons and their juice freeze well. I often freeze lemon segments on trays then free-flow them into bags, or freeze the juice in ice-cube trays. On a hot summer's day these stand in for both ice and lemons in a cooling gin and tonic. Why wait till summer?

Lemon Herb Fritters with Goat's Cheese

Photo / Annabel Langbein Media
Photo / Annabel Langbein Media

Ready in 30 mins
Makes 24 medium or 60 small fritters

1½ cups plain flour
3 tsp baking powder
3 eggs
1 cup chilled soda water or cold water
½ tsp salt
Ground black pepper
1 cup finely chopped mixed soft herbs, such as basil, parsley, chervil or mint
¼ cup lemon juice
Zest of 1 lemon, finely grated
2-3 Tbsp neutral oil, such as grapeseed, for frying

To serve
150g cold-smoked salmon
½ cup sour cream
Sprigs of dill

Combine flour, baking powder, eggs, soda water or water, salt and pepper in a mixing bowl, beating to make a smooth batter. Cover and store in the fridge until ready to cook - up to 4 hours ahead. Just before cooking, stir in herbs, lemon zest and lemon juice. Heat a heavy frypan over medium heat and coat lightly with oil. Cook dessertspoonfuls of mixture, 2-3 at a time, turning to cook the other side as bubbles form in the mixture. Lightly re-oil pan between batches. Transfer cooked fritters to a rack.To serve, top each fritter with a little smoked salmon, a dab of sour cream and a sprig of dill. Accompany with a green salad for lunch or a light dinner, or with a dipping sauce if serving as finger food.

Annabel says: Adding a handful of herbs and some lemon juice transforms a simple fritter batter into a flavoursome canape base - delicious topped with smoked salmon and sour cream or goat's cheese and watercress. If you're making fritters in bulk, you can speed up the process by quickly browning them in the pan and then finishing them in an 180C oven for 8-10 minutes until spongy to the touch.

Lemon Fish Pie

Photo / Annabel Langbein Media
Photo / Annabel Langbein Media

Ready in 45 mins
Serves 4

3-4 Tbsp lemon juice
1 Tbsp finely chopped parsley leaves
500g boneless fish, cut into 4cm chunks
3 hard-boiled eggs, quartered
4 cups mashed potato, seasoned

White sauce
70g butter
½ cup flour
½ tsp mustard powder
A pinch of nutmeg
3 cups milk
Salt and ground black pepper

To make the white sauce, melt the butter in a pot and when it begins to foam, add the flour. Stir over heat for about a minute. Add mustard powder and nutmeg. Gradually whisk in milk, stirring constantly, until a thick, smooth sauce is produced (it will thicken as it cools). Season to taste. Makes 3½ cups. Preheat oven to 220C fanbake. Mix lemon juice and parsley through white sauce. It should taste quite lemony. Pour about half the sauce into a shallow baking dish. Arrange fish and hard-boiled eggs evenly on top, cover with remaining sauce and top with a layer of mashed potato. Bake until sauce is bubbling and potato is golden (25-30 minutes).

Annabel says: This is my all-time, hands-down favourite fish pie - a creamy white sauce bright with lemon juice, mixed with chunks of fresh fish and boiled eggs, topped with creamy mash and baked to golden perfection. You can assemble this pie in the morning and pop it in the fridge ready to bake and serve when you get home.

Limoncello

Photo / Annabel Langbein Media
Photo / Annabel Langbein Media

Ready in 30 mins + steeping
Makes 4 cups

2½ cups vodka
Zest of 8 just-ripe lemons, cut with a vegetable peeler, leaving a little pith on
¾ cup sugar
Juice of 3 lemons, strained
3 whole cloves

Combine vodka and lemon zest, cover and steep for 48 hours in a cool, dark place. Strain. Boil sugar, lemon juice and cloves with 1 cup water until syrupy. Cool, discard cloves and mix syrup into lemon vodka. Serve chilled in shot glasses or with ice and soda.

Annabel says: When our kids were little we took a sabbatical for several months in Italy and Sicily, travelling around farms, discovering the rhythm and traditions of rural life and learning the crafts of the Italian country kitchen. Along with wine and oil and pasta, people there make their own potent grog. Sometimes it is with herbs, such as bay leaves, but in the lemon country around the Gulf of Naples, the tipple of choice is limoncello. Purists will tell you that limoncello should be stored in a hole in the earth to keep it cool, but in my kitchen the dark pot cupboard serves well as a storage place. Enjoy chilled as an after-dinner digestive, or make into a long drink with ice and soda.