Bring a medium sauce pot of generously salted water to a boil. Add the rigatoni and cook until tender, 10 to 12 minutes. Drain, reserving 1 cup pasta cooking water.
While the water heats and the rigatoni cooks, prepare the remaining ingredients and the sauce.

• Peel and thinly slice the red onion.
• Rinse the white beans.
• Zest the lemon.
• Juice the lemon; measure out 2 tablespoons juice.

In a large frying pan over medium-high heat, warm 2 to 3 teaspoons oil until hot but not smoking. Add the onion and as many chile flakes as you like, season with salt, and cook, stirring occasionally, until the onion is softened and beginning to caramelize, 5 to 6 minutes.
Add the beans and reserved pasta cooking water and season with pepper. Bring to a boil, reduce to a simmer, and cook, stirring occasionally, until the liquid is slightly thickened, 5 to 6 minutes. Stir in the arugula, rigatoni, pesto, and lemon zest and juice and cook until the arugula wilts, 1 to 2 minutes. Remove from the heat and season to taste with salt.

Transfer the rigatoni to individual bowls, top with the Parmesan, and serve.

Chef’s tip: To serve the meal, you can either follow Step 3 as written, or stop after the beans have thickened, then stir in the lemon zest and juice and season to taste with salt. Set out the beans, rigatoni, arugula, pesto, and Parmesan and let everyone assemble their own pasta as they please.

Kids can!

• Rinse the beans.
• Juice the lemon.
• Top the pasta with the Parmesan.
• Set the table.
• Compliment the cook.