From Charleton House, a country house hotel in Somerset, England, comes this piquant accompaniment to robust cheddar cheeses with good age and big flavors. We like it, too, with honey-glazed ham, in Christmas turkey sandwiches, or tossed with grilled red peppers. Look for aged cheddars from Vermont, New York State, and England, but always taste before buying. Give the onions two weeks of mellowing. Make up in small crocks or canning jars for giving, or in larger ones for the family. Keeps about 8 weeks in a cool place.
Slow roasting requires rather little effort for the succulent results that are produced. It concentrates the flavor of tomatoes, leaving them intact but meltingly tender.