1 tablespoon canola or olive oil
1 onion, finely chopped
2 garlic cloves, finely chopped
1 (14-ounce) can of chopped tomatoes, or 2 pounds fresh tomatoes, blanched, peeled, seeded, and coarsely chopped
1 pound green beans, topped and cut into 2-inch lengths
Sea salt and freshly ground black pepper
Heat the oil in a large saucepan or frying pan, add the onion, and cook gently for at least 10 minutes, until soft but not colored. Add the garlic and cook gently for another minute or two, then add the tomatoes and stir well. Stir in the beans, bring the mixture to a gentle simmer, and season well. Turn down the heat, partly cover the pan, and cook very gently, stirring frequently, for about 30 minutes, until the beans are fully tender. Season with salt and pepper. If the mixture seems to be in danger of sticking, add a splash of water or stock. Serve warm or cold.