This is a simple layered casserole with three elements: roasted zucchini, a really good homemade tomato sauce and Parmesan.
Roasting, rather than frying the zucchini, allows you to cut down on olive oil and time.
Thanks to Martha Rose Shulman

Screen Shot 2015-07-19 at 9.41.42 AM

6 servings

For the tomato sauce:
2 to 2½ lbs fresh ripe tomatoes
1 tbsp extra-virgin olive oil
1 small onion, chopped
2 to 4 garlic cloves (to taste)
Salt and pepper
1/4 tsp sugar
2 good sprigs fresh basil
1 & 1/2 tbsp chopped fresh basil

For the zucchini Parmesan:
2 to 2¼ lbs zucchini
Salt and pepper
3 tbsp extra-virgin olive oil
½ to 1 tsp red pepper flakes, to taste
¾ to 1 cup freshly grated Parmesan

If you have a food mill, quarter tomatoes. If not, peel, seed and chop them. (See step 5.)

To make the tomato sauce, heat 1 tablespoon olive oil in a large, heavy skillet over medium heat and add onion. Cook, stirring often, until tender, about 5 minutes.
Add the garlic. Cook, stirring, until fragrant, 30 seconds to a minute, and add the tomatoes, salt, pepper, sugar and basil sprigs. Increase the heat to medium-high.

When the tomatoes are bubbling briskly, stir and reduce heat to medium. Cook, stirring often, until the tomatoes have cooked down and are beginning to stick to pan, 15 to 25 minutes, depending on consistency. Remove the basil sprigs; taste and adjust seasoning.
Heat oven to 450 degrees.
Line 2 sheet pans with parchment. Trim the ends off the zucchini and cut in half crosswise, then into lengthwise slices, about 1/4 to 1/3 inch thick. Season on both sides with salt and pepper and toss with 2 tablespoons olive oil. Arrange the zucchini slices on baking sheets in one layer and sprinkle with red pepper flakes. Roast for 12 minutes, until lightly browned and easily pierced with a knife. Remove from the oven and reduce heat to 375 degrees.

If using a food mill, put the sauce through a medium blade. If not, pulse the sauce in a food processor fitted with a steel blade until just coarsely puréed. Stir in the chopped basil.

To assemble the dish, oil a 2-quart gratin with olive oil. Spread 1/4 cup tomato sauce over the bottom of dish. Arrange a third of the zucchini in an even layer over the tomato sauce. Spoon a third of the remaining sauce over zucchini and sprinkle with 1/4 cup Parmesan.
Repeat with 2 more layers, ending with 1/4 cup Parmesan.
Drizzle on the remaining tablespoon olive oil.
Bake 30 to 35 minutes, until bubbling and browned on the top and edges. Remove from the heat and allow to sit for 5 to 10 minutes before serving.