A recipe for eggplant relish in a 1975 issue of Gourmet magazine called for pimiento. A member of the pepper (capsicum annuum) family, pimiento is a heart-shaped red sweet pepper. Capsicum annuum covers a wide variety of peppers including many varieties of pimiento, bell peppers and chiles.
In Tapas (Knopf, $30), Penelope Casas writes that pimiento “is nothing more than the Spanish word for peppers, and in this country we used the word to mean red peppers that are cooked, peeled and packaged in jars or cans.”
Pimientos are similar to red bell peppers, though the flesh of a pimiento is said to be much sweeter. There also is an issue of size. Most culinary resources define pimientos as peppers measuring 3 to 4 inches long and 2 inches wide at the widest part. But some refer to them as the cherry peppers, which are smaller and plumper. So not all pimiento peppers are classified as the same variety.
You are probably most familiar with pieces of pimiento stuffed into green olives. Those pieces have been roasted and the skin removed. It’s a process similar to roasting red bell peppers.
Small (4-ounce) jars of diced pimiento are commonly sold at most grocery stores. In this recipe, it sounds as though they are referring to the larger jarred pimiento peppers. You could substitute jarred roasted red peppers.