Heat 2 tablespoons of the olive oil in a large nonstick skillet. Add the garlic and saute until fragrant, about 1 minute. Add the red pepper flakes
and saute for 20 seconds. Add the spinach
in batches and toss in the hot oil until wilted. Season with salt and pepper and saute until tender, about 6 minutes. Transfer the spinach to a fine-mesh sieve
as it cools. When cool, place in a clean tea
towel and squeeze out excess water. Roughly chop
and reserve in a bowl.
Wipe out the skillet (or use a second large skillet), add the remaining 2 tablespoons olive oil, and set over a medium-high flame. When hot, add the zucchini and cook until tender and golden, about 12 minutes. Remove to a bowl and reserve.
Preheat the oven to 375 degrees F.
Butter a 9-by-13-by-4-inch baking dish
and add a thin layer of besciamella. Cover with a layer of noodles (4 across) and then another thin layer of besciamella. Sprinkle some spinach and zucchini over the besciamella, and then top with one-quarter of the mozzarella, a sprinkling of the Parmesan and a ladleful of red sauce. Repeat this sequence twice to form two more layers. Top with a final layer of noodles
and spread a final layer of besciamella, red sauce, mozzarella
, Parmesan, and a few pats of butter to help the cheese
crisp-up in the oven.
Cover the lasagne
with foil and bake for about 30 minutes. Raise the heat to 400 degrees F, uncover, and bake until the cheese just begins to brown and the sauce bubbles, another 10 to 15 minutes. Let rest for 15 minutes before slicing. Serve with a sprinkling of Parmesan and a drop of extra-virgin olive oil.