Preheat your oven to 350 degrees F and heat your grill to medium. Slice the zucchinis lengthwise, into ¼-inch-thick strips, getting 6 slices out of each zucchini and discarding the ends.
Spray the zucchini slices with olive oil and sprinkle them with ½ teaspoon Kosher salt, ⅛ teaspoon black pepper, and ½ teaspoon garlic powder.
Grill the zucchini slices, in batches, 2-3 minutes on each side, or until golden and firm - not browned and crisp. Spread them on clean kitchen towels to soak up more moisture.
Cook the beef:
In a large skillet, heat the olive oil over medium-high heat, about 2 minutes. Add the meat, the minced garlic, ½ teaspoon kosher salt and ¼ teaspoon black pepper.
Cook, stirring with a wooden spoon to break up the meat, until the meat is no longer raw, about 5 minutes. Drain into a colander, then return the meat to the pot and mix in 1 cup of the marinara sauce. Turn the heat off and set aside.
Prepare the ricotta layer:
In a medium bowl, with a fork, mix together the ricotta, eggs, basil, and the remaining kosher salt and black pepper.
Assemble the lasagna:
Spread the remaining ⅓ cup of the marinara sauce on the bottom of a 9 X 13 baking dish. You can also use a slightly smaller baking dish such as a dish that measures 11 X 7 inches.
Top the marinara sauce with a layer of zucchini, then a third of the ricotta mixture, a third of the meat mixture, and a third of the shredded mozzarella cheese.
Repeat, arranging the zucchini slices in the opposite direction: zucchini, ⅓ ricotta, ⅓ meat mixture, ⅓ mozzarella.
Repeat one last time, adding one extra layer of zucchini: zucchini, ricotta, meat mixture, more zucchini, and mozzarella.
Bake the lasagna:
Bake, uncovered, until the cheese is golden, about 30 minutes. You can finish by broiling for 1-2 minutes on high to brown the cheese, if you wish and if your dish is broiler-safe. Let stand for 10 minutes before serving.
1. Grilling works best to remove the water from the zucchini. But as an alternative to grilling, you can bake the zucchini slices in a 500F oven until golden, about 5 minutes on each side. Or, if your pan is broiler-safe and you use unbleached parchment paper marked as broiler-safe, you can broil them 6 inches from the heating element (not directly below), 3-4 minutes per side. Remember to set the oven to 350F when you're done.2. If you're using truly big zucchinis, ½ lb. each, cut them in half crosswise, then slice lengthwise, as I do in the video. Make sure to save the prettiest slices for the top of the lasagna. 3. You can lightly grease the bottom of the baking dish instead of spreading it with ⅓ cup marinara sauce, as I do in the video.4. You can grill the zucchini ahead of time. Store it in the fridge in an airtight container, separating layers with paper towels. Replace the paper towels after a few hours with dry ones. 5. You can also cook the beef ahead of time and briefly reheat it in the microwave prior to using it in the lasagna.