Preheat oven to 350°F (175°C).
Trim the zucchini and slice into thin rounds about 1/8 inch thick; cut long slices in half so they are 3–4 inches long if desired.
Lay the zucchini slices on paper towels or a clean kitchen towel and sprinkle both sides with kosher salt; let sit 15–20 minutes to draw out moisture.
Heat 2 tablespoons olive oil in a large oven-safe skillet over medium-low heat. Add the cherry tomatoes, minced garlic, and a pinch of salt, and cook, stirring often, until the tomatoes burst and become saucy, about 15–20 minutes. Transfer the tomato mixture to a bowl and set aside.
Wipe the skillet if needed, add remaining 1 tablespoon olive oil, then add the diced onion with a pinch of salt and pepper. Cook over medium heat until softened, about 5 minutes.
Add the ground beef or turkey to the skillet with another pinch of salt and pepper. Brown the meat over medium heat, breaking it into small pieces, until fully cooked; stir in the dried basil.
Stir the reserved burst cherry tomato mixture back into the browned meat until combined.
Pat the zucchini slices dry with paper towels, then arrange them evenly over the meat mixture in the skillet.
Drop spoonfuls of ricotta cheese over the zucchini, then sprinkle the grated Parmesan evenly on top.
Bake in the preheated oven until the top is golden and bubbling, about 30 minutes.
Remove from oven and sprinkle with additional Parmesan, crushed red pepper to taste, and fresh basil leaves before serving.