Place sunflower oil in a deep fryer and heat to 350 degrees F (175 degrees C). Slice zucchini into 1/8-inch rounds.
Add some zucchini to the hot oil and deep-fry until lightly browned, 4 to 5 minutes. Transfer to a single layer on paper towels to drain and repeat to cook remaining zucchini. Let zucchini cool to room temperature.
Transfer cooled zucchini to a bowl. Cover and refrigerate, 8 hours to overnight.
Bring a large pot of lightly salted water to a boil. Cook spaghetti in the boiling water, stirring occasionally, until it's 2 minutes away from being tender yet firm to the bite, 9 to 10 minutes.
As you are cooking the spaghetti, heat olive oil in a skillet over medium heat. Add zucchini and salt and cook, stirring occasionally, until it starts to release juices, soften, and break down, 3 to 5 minutes. Add a couple splashes of the pasta water to the zucchini, but don't overdo it. Break zucchini into small pieces with the edge of a spoon or spatula. Reduce heat to low and toss in basil and butter; stir until butter melts.
Grab spaghetti with tongs and transfer it right into the sauce; stir until coated. Mix in Pecorino Romano and Parmigiano-Reggiano cheeses. Add a final splash of pasta water and adjust salt if needed.
Serve with more grated cheese and fresh basil.
Nutritional Facts
Per 2 servings
Calories: 1016
Carbohydrate: 63g
Fat: 78g
Fiber: 8g
Protein: 23g
Sugar: 12g
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