Even more than most tomato dishes, this uncomplicated gratin excels with high summer tomatoes — late summer is the only time I’ve made it. You might think it would be better to remove the tomato skins, but they help the slices to keep some shape. The herb I add is almost always dried, highly aromatic Greek sage, not too much, but other labiate herbs are also good, including fresh basil, especially if you have your own shade-grown pot. A different option is capers in salt, rinsed. More than once, I’ve served the gratin with a grilled marinated flank steak and this zucchini pudding.