Step 1

Heat oil in a 10" ovenproof skillet over medium. Cook onion, garlic, and cumin, stirring occasionally, until onion is beginning to brown and soften, about 5 minutes. Add both cans of crushed tomatoes, basil leaves, red pepper flakes, and salt. Cook, stirring occasionally, until sauce is slightly thickened and flavors have melded, about 10 minutes. Stir in ½ cup water, then remove from heat.

Step 2

Cook spinach in a medium pot of boiling salted water until wilted, about 30 seconds. Drain and transfer to a large bowl of ice water. Let sit until cool enough to handle. Drain and ring out excess moisture from spinach with your hands. Separate spinach and set aside.

Step 3

Preheat oven to 425°. Cook noodles in a large pot of boiling salted water, stirring occasionally and separating noodles as needed to keep from sticking, until just starting to soften and bend but still firm in the center; about 5 minutes. (They should be firmer than you think they should be, but this will create al dente lasagna layers instead of gummy ones.) Transfer noodles to a large bowl of cold water and let cool. Drain noodles and stack flat on a rimmed baking sheet, separating layers with sheets of parchment or wax paper.

Step 4

Place zucchini in a single layer on a rimmed baking sheet lined with paper towels and salt generously on both sides. Let sit 15 minutes to allow excess moisture to drain.

Step 5

Process ricotta and milk in a food processor until smooth. (It should be whipped and a bit airy). Add pepper, nutmeg, 1½ tsp. Diamond Crystal or 1 tsp. Morton kosher salt, and 4 oz. Parmesan and process 10 seconds. Transfer to a medium bowl and fold in reserved spinach with a rubber spatula.

Step 6

Using a ladle, transfer all but 1 cup sauce to a medium bowl, (there should be just a thin even layer of sauce left behind).

Step 7

Take a lasagna sheet and place 1–2 slices of zucchini in the center. Scoop 2 (heaping) Tbsp. ricotta mixture on top and spread evenly over noodle. Sprinkle 1 Tbsp. mozzarella on top. Carefully roll up lasagna and sit vertically in skillet with tomato sauce. Repeat with remaining lasagna sheets, zucchini, ricotta mixture, and mozzarella.

Step 8

Evenly ladle sauce in bowl over rolled pasta, then sprinkle more Parmesan over. Bake lasagna until sauce is bubbling gently around the edges and tops of lasagna rolls are browned and crisp, 35–40 minutes. Remove from oven and top with more basil to serve.