Aside from the few months each year when truly local, just-picked plum tomatoes are available, the best tomatoes you can buy often come in a can. The reason is that tomatoes destined for the canning plant are picked ripe and red (meaning more real tomato flavor), and processed in very short order. Imported Italian plum tomatoes, especially San Marzanos (a specific Italian variety grown in the Campania region), are especially high in quality. All canned tomatoes come peeled?though you may find bits of peel in lesser quality brands.
One 28-oz. can = about 10 to 12 whole tomatoes (or about 2 pounds); one 14-1/2-oz. can = 5 to 6 whole tomatoes, (or about 1 pound)
Fresh, peeled, plum tomatoes
If buying "San Marzano" be sure the label says San Marzano and not "San Marzano Type" and also that they're imported from Italy. The real deal will have a government seal and the term D.O.P. on the label. A good domestic choice is Muir Glen organic brand.
Some recipes may call for the tomatoes to be drained of their juices. Remove any tough stem ends.
Unopened canned tomatoes will keep a long while in the pantry. Refrigerate the tomatoes after opening them and use within a few days.