The stalwart of sauces and stews is ripe with anti-cancer molecules and builds strong bones• Rosie Sykes' Fish baked with tomato sauce recipe
The larder is worryingly bare when you've run out of tinned tomatoes. They are the cook's comfort blanket, the progenitor of any number of soups, sauces, stews and braises. But brands do vary in quality. There's a school of thought that whole plum tomatoes are better than the chopped sort, because they don't rely on the pulpy centre to create a rich juice. You can easily chop up whole tinned tomatoes without making any inconvenientmess by snipping away at them with kitchen scissors while they are still inside in the opened can. Chopped or whole, choose brands where at least half the tin's contents are tomato flesh, and the juice is nice and thick.
Why are tinned tomatoes good for me?
Tomatoes are the best source of the carotenoid pigment lycopene. Some studies suggest it can help prevent prostate, lung, and stomach cancers. Tomatoes are an interesting exception to the rule that cooking food reduces or destroys valuable micronutrients: lycopene is better absorbed when it has been heated, either during processing or cooking, as the heat turns the molecule into more useful isomers. Tomatoes provide significant amounts of bone-strengthening vitamin K, and some research suggests that lycopene also supports bone health. Many studies link tomatoes with heart benefits, and although the mechanisms aren't yet clear, the antioxidant vitamins C and E in them, along with lycopene, seem to slow down the processes that would eventually cause heart disease.
Where to buy and what to pay
Prices vary wildly from 31p-£1.34 per 400g tin. The cheapest may be a false bargain if they are watery and tinny tasting.It's worthwhile sampling a few brands to identify the best value for money. When you hit on your favourite, look out for packs of four: often they work out cheaper.
Joanna Blythman is the author of What To Eat (Fourth Estate, £9.99). To order a copy for £7.99 with free UK p&p, go to guardianbookshop.co.uk
Fish baked with tomato sauce
The tomato sauce in this dish is super versatile. I always have a stock in my freezer to put on pasta, pizza or meat.
3 tbsp olive oil
3 medium red onions, finely sliced
4 garlic cloves, crushed
1 large red chilli, deseeded and finely sliced
1 tbsp sherry vinegar
400g chopped tomatoes
3 tbsp water
1 bay leaf
2 sprigs of thyme
½ tsp salt
1 tsp sugar
1 tbsp capers
A small bunch of basil, chopped
4 x 170g firm white fish
1 Heat 2 tbsp oil in a shallow pan over a medium heat. Add the onions and cook for 15 minutes, stirring now and then, until soft and lightly browned. Add the garlic and chilli. Stir for a few minutes, add the vinegar and leave to evaporate.
2 Add the tomatoes, water, herbs, salt and sugar, bring to the boil. Lower the heat and leave to simmer, uncovered for 30 minutes to 1 hour, stirring occasionally, until it has almost reduced to a paste.
3 Take off the heat, fish out the herbs, stir in the butter, and season to taste. Blend until smooth. Stir in the capers and chopped basil.
4 Preheat the oven to 200C/400F/gas mark 6. Oil an ovenproof dish. Lie the fish in side by side. Season on both sides. Cover the fish with tomato sauce, drizzle over the rest of the oil. Place in the oven and bake for about 15 minutes, until the fish is cooked.
Rosie Sykes is head chef of Fitzbillies and co-author of The Kitchen Revolution (Ebury Press, £25). To order a copy for £19.99 with free UK p&p, go to guardian.com/bookshop
Photo - Tinned tomatoes: the cook's comfort blanket - and good for your bones and your heart. Photograph: Jill Mead for the Guardian