San Marzano gets all the attention, and it deserves a fair bit of it, but the supermarket habit of treating “tomato” as one ingredient does real damage to cooking. A tinned plum tomato, a ripe heirloom in August, and a punnet of supermarket salad tomatoes in February are barely the same food. Knowing which tomato does which job is the difference between a sauce that tastes of summer and one that tastes of the tin.
Here are the ones worth knowing, and what to do with each.
San Marzano (and why the tin often beats the fresh)
The famous plum tomato from the volcanic soil south of Naples. Low in seeds and water, high in sweet flesh, which is exactly what you want in a long-cooked sauce. The thing most people miss is that a good tinned San Marzano, picked and canned at peak ripeness, will beat a fresh tomato that travelled for a week and ripened in a lorry. For sauce, the tin is not a compromise. It is often the right answer. Look for the DOP stamp, and ignore the imitators that just borrow the name.
Roma and other plum tomatoes
The everyday workhorse. Meaty, low-moisture, cheaper than San Marzano and perfectly good for sauce, roasting, or anything cooked down. If you are making a weeknight sugo and not chasing a specific flavour, Roma plums are the sensible buy. They roast beautifully, concentrating into something jammy and sweet.
Datterino and cherry tomatoes
Small, intensely sweet, high in flavour even out of season because the sugar-to-size ratio is forgiving. These are the ones to reach for when the big tomatoes are hard and pink in winter. Halve them, roast them hot and fast with a good olive oil and salt, and they collapse into a quick sauce with more life than anything you could build from a sad beefsteak in January.
Heirlooms (Brandywine, Black Krim, Green Zebra)
The summer treat, and a waste of money to cook. These are for eating raw at room temperature, sliced thick, salted with a flaky finishing salt, maybe a little oil and nothing else. Cooking an heirloom destroys the complex flavour you paid for and turns it watery. Buy them in season, eat them cold, do not apply heat.
The supermarket salad tomato
Bred to survive shipping and look red, not to taste good. In winter they are firm, pink at the core, and flavourless. If that is all you can get, do not eat them raw. Roast them hard to drive off the water and force some sweetness out, or skip fresh entirely and cook from a tin. There is no shame in the tin.
A note on pizza
On a pizza the tomato is doing a lot of work with very little time in the oven, so a bright uncooked passata of good tinned tomatoes usually beats a heavy cooked sauce. This matters more than people think across the different pizza styles, where a Neapolitan in particular wants little more than crushed San Marzano and salt.
What we keep
A few tins of DOP San Marzano in the cupboard for proper sauce, cheaper Roma tins for everyday, and a habit of buying small sweet tomatoes when the big ones look dead. In high summer, heirlooms, eaten raw and never cooked. The variety on the label is not a detail. It is the recipe.