I’ve mostly cooked tomatoes on the stove, perhaps a few times on the grill but rarely in an oven, and probably not so for over a couple of hours. A friend of mine who likes to dry fruits and vegetables, sometimes in an oven and sometimes in a special dryer, said that even she hadn’t heard of slow-roasting tomatoes in the oven – it is not a common method but extracts and concentrates the flavor of the tomato in an uncommon manner.
In cooking tomatoes, some methods remove the skin and gel of seeds to obtain smoother texture and to reduce water; some methods use all of it; some modern methods use just the gel of seeds for its aesthetic appeal; and yet some methods cook the pulp separately from the gel of seeds, and then combine the extracts after filtering. The pulp contains most of the fruit sugars – which invariably gets used up the longer the tomato stays off the vine – while the gel of seeds contributes to the acidity1. Different varieties of tomatoes contain different proportions of sugar to acid, and in some southern states of North America and in parts of India even green unripe tomatoes are used in cooking.
Here’s a method to slow roast tomatoes in an oven:
Tomatoes – the best and freshest you can find.
Oil – light-bodied olive oil or any other similar oil.
Salt and pepper.
Wash and dry tomatoes, and cut them into halves before placing them in a single layer on a parchment-lined baking sheet. Grind garlic with oil and use the paste to coat the tomato halves generously. Sprinkle some thyme and season with salt and pepper. Place in a 250˚F oven and check every half hour or so. Depending on the size, water content, and number of tomatoes the roasting time might vary - adjust temperature accordingly. The tomatoes are considered done when they have shrunk in size, developed a deep brown to golden caramelized top, and still retain some moisture. Let the tomatoes cool-down before using them as is or skin removed to form the base of a sauce among other things.
It seems to be widely acknowledged that about 70 years ago people recognized and started to cultivate a variety of tomato that was uniformly red and regularly shaped unlike the older heirloom varieties that appear in different shades and irregular shapes. A botanist recently described how this recent variety that has become commercially popular arises due to a mutation that not only results in the observed traits but also reduces the sugar content by around 30% 2. The majority of sugar in tomatoes still arrives from photosynthesis that occurs in leaves2 making one think about the extent of flavor in vine-ripened tomatoes and vine-ripened heirloom tomatoes in particular.
Tomatoes are such an esteemed part of Italian cuisine that they are referred to as pomodoro or ‘golden fruit’. And, given the extent to which tomatoes are featured in this cuisine I would not have guessed that tomatoes in Italy were just a recent occurrence relative to the history of tomatoes. Tomatoes have been grown since many thousands of years in Central America but only in the 16th century were they imported to Europe where they were initially considered poisonous before being called the ‘love apple’ in English in the 18th century, and before returning to colonized North America to be used the way they were used in Europe3. How were tomatoes used in native Central American recipes ?
1. On food and cooking by Harold McGhee.
2. How Tomatoes Lost Their Taste by Kai Kupferschmidt, News article in Science 28 June 2012, referring to the paper: Uniform ripening Encodes a Golden 2-like Transcription Factor Regulating Tomato Fruit Chloroplast Development by Powell ALT et al. Science 2012 Vol. 336 no. 6089 pp. 1711-1715.
3. Food: The history of taste edited by Paul Freedman