Zucchini Lasagna

Heat oil in a large skillet over high. Add sausage, 1 teaspoon of the salt, and 1/4 teaspoon of the pepper; cook, using a wooden spoon to break up sausage, 3 minutes. Stir in onion and garlic; cook, stirring occasionally, until fragrant and tender, about 3 minutes. Add tomatoes; bring to a boil. Reduce heat to low; cover and simmer, stirring occasionally, 20 minutes. Uncover and stir in basil. Continue simmering, uncovered, stirring occasionally, until slightly thickened, about 10 minutes. Remove from heat.

Preheat oven to broil with rack positioned 6 inches from heat source. Slice zucchini lengthwise into 1/8-inch-thick slices using a mandoline (about 40 slices total). Arrange zucchini evenly in a single layer on 3 rimmed baking sheets. Sprinkle evenly with 3/4 teaspoon of the salt; let stand 5 minutes. Blot zucchini with paper towels.

Broil zucchini in batches, if needed, in preheated oven for 2 minutes per batch. Remove from oven; reduce oven temperature to 375°F.

Stir together ricotta, Parmigiano-Reggiano, egg, and remaining 1/4 teaspoon each salt and pepper in a bowl. Spread one third (about 1 cup) of the sausage sauce in bottom of a 13- x 9-inch baking dish. Layer one fourth of the zucchini over sauce to cover bottom of dish. Spread one third (about 2/3 cup) of the ricotta mixture over zucchini; sprinkle with one fourth (about 1 cup) of the mozzarella. Top with one fourth of the zucchini; layer with one third of the sausage sauce, one third of the ricotta mixture, and one fourth of the mozzarella. Repeat layers once. Layer top with remaining zucchini. 

Cover baking dish with aluminum foil; bake in preheated oven 30 minutes. Remove foil; bake 15 minutes. Sprinkle with remaining 1 cup mozzarella; bake until bubbling and cheese is melted, about 15 minutes. Let stand 10 minutes. Serve.