Bring a large pot of salted water to a boil. Add the pasta and cook according to package instructions until al dente.

Meanwhile, heat the oil in a large skillet over medium-high. Add the walnuts and cook, stirring, until golden and fragrant, about 1 minute. Using a slotted spoon, transfer walnuts to a small bowl. Season walnuts with a little salt and pepper.

Add the cauliflower and chile flakes to the skillet and toss to coat in the oil. Shake the skillet so cauliflower settles in an even layer. Cook, undisturbed, 2 minutes. Toss and shake to arrange in an even layer again and cook, undisturbed, another 2 to 3 minutes; season with salt and pepper and remove from heat.

Drain pasta and add to the skillet along with the lemon zest, cheese, toasted walnuts, and half the mint; toss to combine. Divide among plates or bowls and top with remaining mint, more cheese and a drizzle of olive oil. Squeeze the juice of half a lemon on top.