All sweetness under the skin Those pallid out-of-season vegetables can be much improved by a long spell in a slow oven, says Annie Bell

They can all come to the party - even the tomatoes usually shunned at this time of year for their lack of fragrance. And the aubergines, and the peppers. Not only will baking or roasting work wonders for the seasonal likes of beetroot, red and whi te onions and sweet potatoes, it affords an ideal treatment for the under-par, out-of-season vegetables, as well.

Tomatoes will endure long hours in a low oven, when their sweetness and flavour will slowly be drawn out until they are caramelised at the edges, skins wrinkled, sitting in a pool of sticky roasting juices. Having the patience of a fire-fly, I tend to set the timer for an hour and a half at a higher temperature, but rest assured: even really horrible, not-fit-for-a-salad tomatoes will respond to this approach.

I can date my conversion back to a meeting with a gardener in Provence. He is intent on relying as far as possible on the produce of his garden throughout the year. Spring will find him sowing, summer eating like a king, autumn madly preserving, drying and bottling, but come winter he will need all the imagination he can muster. His way of coping is to bake and roast any vegetables that lend themselves to it.

The stuffed vegetable items that line the posh deli counters are convenient enough for picnics, but I have my reservations. Starchy stuffings absorb vegetable juices as they cook; the result tends to be a flaccid vegetable casing and stodgy interior. I prefer to bake or roast vegetables and to embellish them afterwards.

For roasting tomatoes, and vegetables such as peppers, aubergines, fennel and sweet potatoes, the requisites are chunky sea salt, ground black pepper, a fruity olive oil and honey if you want to accentuate the sweetness. n If you are roasting a selectiontogether, consider tucking a whole head of garlic, its top sliced off to reveal the cloves, and a whole red chilli or two between them. Any juices you acquire during the process of cooking provide a matchless base for a dressing, with a depth of flavourthat could not be achieved any other way.

Beetroots bake in their own skin to a precocious sweetness that has more in common with a fruit than a vegetable. The answer is to take them down a peg or two with a splash of red wine vinegar - anoint them once baked and peeled, along with some olive oil, and leave them for 30 minutes, then mix in some snipped chives and chervil and serve with a fresh goat's cheese.

Orange-fleshed sweet potatoes go one step further, given long enough in the oven, if you slip off their skins they will be coated in a dark slice of caramel - a ginger-soy-sesame trio works a treat with these.

Does anyone bake their onions in the embers of a fire nowadays? To my mind, the suburban hearth fails in its appeal. In Honey from a Weed, Patience Gray describes a pre-spring festival in Catalonia "held in the open air under the almond trees in flower, and sometimes in the snow".

Onion shoots are roasted over vine cuttings, slipped from their burnt exterior and eaten with a sauce called Salvitxada: "2oz grilled almonds, 2 grilled cloves of garlic and 1 ungrilled, a pinch of paprika, a little chopped parsley and mint, salt, 1 grilled tomato, skinned, vinegar if you like, olive oil. Pound the above in a mortar, beginning with the almonds, and finally lubricate with a little olive oil; the sauce should not be thick."

Soups made with roasted vegetables are effortless: puree some roasted fennel and flat-cap mushrooms with vegetable stock and a spoon of creme fraiche, and serve it with some Vacherin Mont D'Or (the sort of cheese that makes a trip to the cheese shop worthwhile) in the centre.

On reflection, my gardener friend is probably not having nearly such a bad time of it after all.

Baked red onions with Sicilian crumbs Serves 4

Ingredients: 3lb (1.35kg) red onions 3tbs extra virgin olive oil 4 salted anchovy fillets, coarsely chopped 1 level tsp red chilli, minced 3oz (85g) white breadcrumbs finely grated zest of 1 lemon 1 heaped dsp capers, rinsed and coarsely chopped 6 mint leaves, finely chopped salt, pepper 3/4 oz (85-110g) unsalted butter Preparation: Preheat the oven to 160C/325F/gas 3 and bake the onions, unpeeled, for 1hr 15min. While they are cooking, heat the olive oil in a frying pan, add the anchovies and chilli and mash into the oil, then add the breadcrumbs and cook, stirring, until they are golden and crisp.

Then transfer them to a bowl and mix in the lemon zest, capers and mint.

When the onions are cooked, slice off one end of each, squeeze the inside from its skin, arrange in a dish and slice them open. Season and dot with butter, let this begin to melt, then scatter over the crumbs and serve.

Roasted tomatoes and aubergine with cannellini beans Serves 4

Ingredients: 1 aubergine 2lb (900g) tomatoes (6-7oz each)

2 red chillies 1/2 a head of garlic 1dsp clear honey 6tbs extra virgin oil salt, pepper 6oz (170g) cannellini beans, soaked overnight 15 saffron filaments 1dsp red wine vinegar 1 heaped tbs flat-leaf parsley, finely chopped Preparation: Preheat the oven to 160C/325F/gas 3. Cut aubergine into 2in rounds and quarter, cut a cone from each tomato to remove the core, and halve. Arrange aubergine, tomatoes, chillies and garlic in a roasting dish. Drizzle over the honey and olive oil and season. Roast for 1hr 30min, basting occasionally.

Discard the chillies, squeeze the garlic cloves from their casings and transfer the vegetables to a serving dish, leaving juices in the pan.

You need to cook the beans at the same time as the vegetables: put them in a flameproof casserole and cover with water by 2in. Do not add any salt. Bring the beans to the boil on top of the stove and skim off any surface foam. Cover the casserole and place in the oven for 1hr 30min or until beans are soft; drain and mix them in with the roasted vegetables.

Heat the saffron filaments in a spoon over a flame until they begin to darken, grind them in a pestle and mortar and blend with 1dsp boiling water. Blend this and the red wine vinegar with the roasting juices, adjust seasoning and pour over the vegetables and beans; scatter over the parsley. Serve warmish or at room temperature.

n Baked sweet potatoes with ginger and sesame seeds Serves 4

Ingredients: 2lb (900g) orange-fleshed sweet potatoes (approx 6oz/170g each)

groundnut oil for frying 2in piece of root ginger, skinned and cut into fine square strips 4tbs light sesame oil (or 2tbs each of dark sesame oil and groundnut oil)

1tbs light soy sauce salt 1 heaped tbs sesame seeds, toasted Preparation: Preheat the oven to 160C/325F/gas 3. Wash and dry the potatoes and bake them for 1hr 30min. While they are cooking, heat some oil in a frying pan and cook the ginger until the strips are dry and beginning to colour: remove with a slotted spoon and drain on absorbent paper. Combine the sesame oil and reserve.

When the potatoes are cooked, the skins should slip off easily. Thickly slice the flesh and arrange on a serving plate. Season with salt, pour the sesame-soy mixture over, and scatter over the sesame seeds and strips of ginger. Serve straight away.