Preheat oven to 350 degrees F.
Heat the olive oil in a large oven-proof skillet or pot over high heat. When the oil shimmers, add the onion and cook until fragrant, about 3 minutes. Add the garlic, cook another minute.
Stir in the passata, 2 1/2 cups water, red pepper flakes, oregano and a pinch each of salt and pepper. Then add the pasta. The key is to be sure all the pasta is covered in the liquid so add a bit of water if needed. Increase the heat to medium-high. Bring the mixture to a boil. Stir frequently until the pasta is al dente, about 8-10 minutes.
Remove the pot from the heat and stir in the ricotta, 1/2 cup parmesan and 1 1/2 cups mozzarella and kale. If needed, tranfer to baking dish and sprinkle the top with remaining parmesan and mozzarella.
Transfer the baking dish to the oven and bake 20-25 minutes or until the cheese has melted and is lightly browned on top. Before serving, cool for 5 minutes. Garnish with some chopped basil and enjoy.