Cooking tomatoes for a long time at a low temperature dehydrates them and concentrates their flavor. These are plumper and softer than commercial sun-dried tomatoes, with a delicate, rich flavor.
Sprinkle cut sides of tomato halves with kosher salt. Place tomato halves, cut sides down, on paper towels. Let stand 1 hour.
Preheat oven to 300°.
Arrange tomato halves, cut sides up, in a single layer on a baking sheet. Bake at 300° for 3 1/2 to 4 hours or until edges of tomatoes curl (the tomatoes will feel dry to the touch).
Note: These will keep for a week, covered, in the refrigerator, or for up to a month in the freezer.