Heat the olive oil in a wide pot over medium heat. Add the onion and cook for 5 minutes until just translucent. Add the diced zucchini and season with salt. Cook for 35–40 minutes over medium-low to medium heat. Stir occasionally. You don't want the zucchini to brown. Instead, you want the liquid to be released slowly and then evaporate to create a thick, jammy texture.

Heat the oil in a skillet over medium-high heat. Pat the zucchini slices dry thoroughly. Once the oil is hot, add the zucchini in batches, and cook for 1–2 minutes per side until golden brown. Transfer to a paper towel-lined plate and set aside.

Taste the sauce and season with salt and pepper. Add the lemon juice and the minced basil and cook for 3–4 minutes.

Add the pasta cooking water and turn the heat to medium-high. Once the sauce is bubbling, add the cooked pasta and toss to coat. Cook for 1 minute. Taste and season once more to your preferences. Turn off the heat.

Divide the pasta between shallow bowls. Garnish with the reserved zucchini chips and lemon zest. Add a few basil leaves on top, if you like.