The bell pepper is the chilli that lost its fire, and the whole of its story turns on that single fact. It is not a separate species from the cayenne or the jalapeño but the same one, Capsicum annuum, and what divides the sweet pepper from the hot is a mutation at one gene. The Pun1 locus governs the enzyme that builds capsaicin in the placental tissue of the fruit; where a recessive, non-functional copy is inherited from both parents, the plant makes no capsaicin at all, and the pepper is sweet. Everything else about the sweet pepper follows from that: because it carries no heat, it can be eaten in quantity as a vegetable rather than in pinches as a spice, and so it was bred for size, for wall thickness, and for flesh, until it became the blocky, hollow, glossy fruit of the modern kitchen.

The species was domesticated in Mesoamerica, and the archaeological record of the Tehuacán valley and the Mexican highlands carries Capsicum annuum back some eight thousand years. But it is important to be exact about what Mexico did and did not do: the peoples of Mesoamerica domesticated the species and selected it, overwhelmingly, for pungency, breeding the great family of chillies on which their cooking rests. The large, thick-walled, wholly sweet pepper is not a Mexican creation. It was after 1493, in the gardens and market plots of Spain, Italy, the Balkans, and Hungary, that European growers found the non-pungent mutants, liked them, and bred them up into a vegetable; the bell pepper as the world now knows it is a European selection from an American plant.

Because of this, the sweet pepper has one species but several distinct cultivar traditions still current in the kitchen, and they are not interchangeable: the blocky Grossum bell of the supermarket; the long, tapered, thin-walled Italian corno di toro and the Hungarian TV paprika; the small, squat, sweet Spanish piquillo of Lodosa; the fleshy Balkan kapia grown for roasting; and the dried, brittle peperone crusco of Senise. Beside all of these stands a genuinely separate lineage: the non-pungent forms of Capsicum chinense, an Amazonian species quite distinct from C. annuum, whose sweet, aromatic little fruits are the ají dulce, cachucha, or ajicito that flavour the sofrito of Puerto Rico, the Dominican Republic, Cuba, and Venezuela. They carry all the fruity perfume of the habanero, their fiery cousin, and none of its heat.

The sweet pepper's voyage is the same voyage as the chilli's, made at the same moment and in the same ships, and yet it became a different journey because the sweet pepper travelled as a vegetable and the chilli as a spice. When Columbus carried Capsicum back to Spain in 1493, what he brought was the whole variable species, hot fruits and mild ones together, and it was in the kitchen gardens and monastery plots of Iberia that European growers began to notice, keep, and multiply the plants that bore no heat. Because a spice can be dried, ground, and shipped in a sack, the pungent chilli raced along the Portuguese and Spanish trade routes to Africa, India, and the Far East within a few decades. The sweet pepper, being watery and perishable and useful only fresh, moved far more slowly and stayed, for its first two centuries, a Mediterranean and Central European vegetable.

Within that world it was taken up with enthusiasm and bred into local shapes. Spain raised the piquillo of Navarre and the sweet pimiento that would be dried and ground for pimentón; Italy made the corno di toro and the peperonata of the summer table, and in Basilicata dried the thin-walled peperone di Senise into the brittle crusco. Carried east by Ottoman power, the pepper reached Anatolia and passed with the Turkish armies up the Danube into Hungary and across the Balkans, where it found the soils and the long hot summers that suited it best; the Hungarians made it their national vegetable and their national spice at once, and the Serbs and Macedonians built around the roasted kapia the great autumn ritual of ajvar. Spanish and Portuguese ships took it south across the Mediterranean into the Maghreb, where the roasted and peeled pepper became the basis of a whole family of cooked salads, and down the Atlantic coast to West Africa, where blended red peppers became the foundation of the Yoruba stew base.

Its return to the Americas came by a separate road. The sweet Capsicum chinense of Amazonia, the ají dulce, spread through the Caribbean, where it joined onion, garlic, and culantro in the sofrito that is the flavour base of the entire Hispanic Caribbean; and from the Spanish Caribbean that habit of building a dish on a fried aromatic base travelled to Louisiana, where the French mirepoix was reworked with the local sweet pepper in place of the carrot to make the holy trinity of Creole and Cajun cooking. In the twentieth century the bell pepper became at last a global vegetable, carried into Chinese stir-frying and the cooking of half of Asia, and, most decisively, into the glasshouses of the Netherlands, whose hydroponic industry now supplies much of the world with the year-round red, yellow, and orange peppers that no market before the nineteen-eighties could have offered.

The bell pepper is now one of the most widely grown vegetables on earth, and one of the very few whose modern form owes as much to horticultural technology as to cookery. China is by a wide margin the largest producer, followed by Mexico, Turkey, Indonesia, and Spain; but the trade that shaped the pepper on the northern European shelf is Dutch. The glasshouse growers of the Westland, working hydroponically under glass and lamps, turned the bell pepper into a year-round crop of uniform size and brilliant colour, and it is to them that the familiar traffic-light trio of green, yellow, and red owes its ubiquity. The colours are not varieties but stages: a green pepper is simply an unripe one, and left on the plant it will turn yellow, orange, red, or purple according to its cultivar, growing sweeter and richer in vitamin C as it goes.

In the kitchen the sweet pepper does three quite distinct jobs. Fresh and raw it is a salad and crudité vegetable, crisp and watery and mild. Cooked slowly with oil, onion, and tomato it collapses into the great family of Mediterranean pepper stews: the peperonata of Italy, the pisto of Spain, the piperade of the Basque country, the lecsó of Hungary, the chakchouka and taktouka of the Maghreb. And roasted until the skin blisters and lifts, then peeled, it becomes something else entirely, silky and smoky and intensely sweet, the basis of the Balkan ajvar, the Catalan escalivada, the Tunisian mechouia, and a hundred marinated antipasti. Its hollow shape invites a fourth use, as a vessel: stuffed peppers, filled with rice and meat and baked in tomato sauce, are a dish of the Ottoman world, the Balkans, Iran, Hungary, and, by way of European emigration, of the United States.

Alongside the fresh vegetable, the dried and ground sweet pepper is a major spice in its own right: the sweet paprika of Hungary and the pimentón of Spain are both made from non-pungent cultivars, and they are the colouring and the backbone of goulash, paprikash, chorizo, and a great deal of Iberian and Central European cooking. And in the Hispanic Caribbean the small sweet ají dulce, a wholly different species, remains the irreplaceable aromatic of sofrito. From a mutation that switched off a single enzyme, the sweet pepper has become salad, stew, sauce, spice, and vessel across most of the world's kitchens.