Bring a medium sauce pot of generously salted water to a boil. Add the rigatoni and cook until just tender, 5 to 6 minutes. Drain, reserving ½ cup pasta water, and set aside.
While the water heats and the rigatoni cooks, prepare the chicken and vegetables.

• Cut a small corner from the chicken packaging and drain off any excess liquid. Transfer to a plate; pat dry with a paper towel. Season generously with salt and pepper.

In a large frying pan over medium-high heat, warm 1 to 2 tablespoons oil until hot but not smoking. Add the chicken and cook, stirring once or twice, until lightly browned but not yet cooked through, 3 to 5 minutes. Transfer to a plate. Do not clean the pan.
While the chicken cooks, start preparing the vegetables.

• Peel and thinly slice the yellow onion.
• Finely chop, press, or grate enough garlic to measure 1 teaspoon.
• Remove the stems, ribs, and seeds from the bell peppers; cut the peppers into ¼-inch-wide strips and then in half crosswise, if desired.
• Strip the kale leaves from the stems.
• Coarsely chop the kale leaves.

In the same pan used for the chicken, if dry, add 1 tablespoon oil and warm over medium-high heat until hot but not smoking. Add the onion, season with salt, and cook, stirring occasionally, until softened and lightly browned, 3 to 5 minutes. Stir in the garlic and as many chile flakes as you like and cook until fragrant, about 1 minute. Add the bell peppers, kale, and chicken and cook, stirring occasionally, until the peppers start to soften, the kale wilts, and the chicken is cooked through, 3 to 5 minutes.

Add the rigatoni and ½ cup reserved pasta water to the pan and cook, stirring occasionally, until the sauce is thickened and the rigatoni is warmed through, 1 to 2 minutes, adding more pasta water if needed to create a good sauce consistency. Remove from the heat and stir in the pesto and Parmesan. Season to taste with salt and pepper.

Transfer the pasta to individual bowls and serve.