Aside from the few months each year when truly local, just-picked plum tomatoes are available (July through September in most regions of the United States), the best plum tomatoes you can buy are those in a can.
True, there are brimming bins of plum tomatoes year-round in many markets, but one taste is all you need to know that these pale, firm impostors have very little real tomato flavor. Sources at the California Tomato Growers Association explain that these so-called fresh tomatoes have been bred to be thick-skinned, tough, and dry enough to withstand the long voyage to markets across the country. Tomatoes destined for the canning plant, on the other hand, are picked ripe and red (meaning more real tomato flavor), and they're peeled and processed in very short order—one estimate is that less than six hours pass from when a tomato is picked until it´s canned.
When you substitute canned for fresh, choose whole, peeled tomatoes. Stay away from crushed, diced, stewed, or any other more processed forms (unless specifically called for in the recipe) as these are typically made from lesser quality tomatoes and have a more cooked, tomato-paste-like flavor. All canned tomatoes come peeled—though you may find bits of peel in lesser quality brands.
Use the following guidelines when substituting canned tomatoes for fresh:
- One 28-ounce can of tomatoes equals about 10 to 12 whole tomatoes, peeled (or about 2 pounds)
- One 14-1/2-ounce can of tomatoes equals 5 to 6 whole tomatoes, peeled (or about 1 pound)