I love this recipe because it's low maintenance, so I can put it in the oven and then finish odd tasks around my apartment while it cooks (as long as I set my timer to remind myself). There's something comforting about digging up the thick pieces of lasagna noodles smothered in garlicky red sauce. Plus, the spinach makes me feel like it's a little bit healthy.
Technique tip: Grating the garlic helps distribute it more evenly in the sauce.
Heat the oven to 425 F. In a 9- by 13-inch baking dish, pour in the crushed tomatoes, 2 teaspoons salt, garlic, red pepper flakes, harissa, if using, and 2 tablespoons olive oil; stir well to combine. Break up the lasagna noodles and submerge them as best you can in the sauce.2.
Cover tightly with foil and bake in the oven for 25 minutes, until the noodles are tender to the bite. Remove, season to taste with salt, then stir in the spinach, mix in half the Parmesan and half the mozzarella. Layer the remaining Parmesan and mozzarella on top.3.
Bake in the oven, uncovered, until the mozzarella is melted and the sauce bubbling, about 20 minutes more. Drizzle with oil, more cheese, the herbs and serve.