Prepare the Zucchini
Slice zucchini evenly.
Sprinkle lightly with salt and let sit for 10 minutes.
Pat dry thoroughly with paper towels to remove excess water.
Optional: Pre-sauté zucchini in olive oil for 3–4 minutes to soften slightly and improve texture.
Make the Cheesy Filling
In a bowl, whisk together ricotta, eggs, milk, salt, pepper, and nutmeg.
Fold in mozzarella and Parmesan until evenly combined.
Adjust seasoning if needed.
Assemble the Casserole
Preheat oven to 375°F (190°C).
Grease a 9×13-inch baking dish.
Spread a layer of zucchini on the bottom.
Spoon half of the cheesy mixture over zucchini.
Repeat layers and smooth the top.
Sprinkle extra mozzarella or Parmesan on top if desired.
Bake
Bake uncovered for 35–40 minutes until top is golden brown and bubbling.
Let rest for 10 minutes before slicing to help the casserole set.