Cook pasta according to package instructions then drain and reserve one cup of pasta water.
Heat 3 tbsps of olive oil in a large skillet over medium heat. Once the oil is hot, add the onions then sauté until softened and fragrant, about 6-8 minutes, stirring occasionally.
Add the diced zucchini, salt, black pepper, and red pepper then stir to combine and continue cooking until zucchini are just starting to soften, about 8-10 minutes, stirring occasionally. Reduce heat to very low until you add the cooked pasta (step 4).
Meanwhile, combine the remaining 2 tbsps olive oil, basil leaves, parmesan, garlic, and lemon zest in the bowl of your mini food processor then pulse until smooth.
Add cooked pasta, pasta water, ricotta, and basil mixture to the skillet with the zucchini then increase the heat to medium-low. Stir to combine everything then let cook until ricotta melts and turns into a creamy sauce. Bring the mixture to a low boil then reduce heat to low and let simmer for about 5 minutes to thicken.
Divide pasta between bowls then top with extra parm and enjoy!