Bring a pot of salted water to a boil. Add the rigatoni and cook, stirring occasionally, until just tender, 10 to 12 minutes. Drain, reserving ½ cup pasta water. While the rigatoni cooks, prepare the pine nuts and breadcrumbs.

In a pan over medium-low heat, warm 1 to 2 teaspoons oil until hot but not smoking. Add the pine nuts and breadcrumbs and toast, stirring frequently, until lightly browned, 2 to 3 minutes. Transfer to a plate and season to taste with salt. Wipe out the pan.

• Cut half the lemon into thin wheels; cut half into wedges.
• Cut the cauliflower into small florets.

In the same pan, warm 1 teaspoon oil over medium-high heat until hot but not smoking. Add the lemon wheels and cook until browned, 2 to 3 minutes per side. Transfer to a work surface to cool, then coarsely chop.
While the lemon wheels cool, add 1 tablespoon oil to the pan and warm until hot but not smoking. Add the cauliflower, season with salt, and cook, stirring occasionally, until browned and just tender, 6 to 8 minutes. While the cauliflower cooks, prepare the remaining ingredients.

• Finely chop enough garlic to measure 1 teaspoon.
• Rinse the capers.
• Strip the rosemary leaves from the stems; coarsely chop the leaves.

Return the chopped lemon to the pan along with the garlic, capers, rosemary, and as much Aleppo pepper as you like. Cook until fragrant, 2 to 3 minutes. Add the rigatoni and the reserved pasta water, and cook, stirring occasionally, until the liquid is absorbed, 2 to 3 minutes. Remove from the heat; stir in the arugula and Italian cheese blend. Season to taste with salt and pepper.

Transfer the pasta to individual bowls. Sprinkle with the pine nuts and breadcrumbs. Serve with the lemon wedges.