Step 1

Warm olive oil in a large skillet over medium heat. Add the spinach with a pinch of salt, and cook, stirring occasionally, until wilted (about 3 minutes). Let spinach cool, then place on two layers of paper towels. Bring the corners of the paper towels up around the spinach and squeeze out as much liquid as you can over the sink.

Step 2

Finely chop the drained spinach, then add to a big bowl with the remaining cheese mixture ingredients. Stir to combine, then season to taste with salt.

Step 3

Meanwhile, spread out zucchini slices on a large cutting board and sprinkle each slice with a little salt. Let sit for 15 minutes, then blot away any excess moisture with a paper towel.

Step 4

Preheat the broiler to high. Place slices on a parchment-lined baking sheet in an even layer (you may need multiple baking sheets). Brush zucchini with olive oil, then working in batches, broil zucchini until tender and golden in spots (about 10 minutes per batch). Flip zucchini slices halfway through cooking.

Step 5

Switch oven temperature to 400°F.

Step 6

Spread 1/3 of the tomato sauce in an even layer in the bottom of a 9 x 13 baking dish. Top with 1/3 of the zucchini, arranged in an even layer. Top the zucchini with 1/2 of the cheese mixture. Repeat even layers two more times with remaining ingredients (so you’ll finish with a layer of zucchini on top). Top evenly with mozzarella and Parmesan cheese.

Step 7

Cover with foil and bake for 30 minutes. Remove the foil, then bake until the cheese is melty and golden on top (about 15 minutes more). Let cool for 10 minutes before serving.