• Bring a large pot of salted water to a boil over high.
• Meanwhile, cut cauliflower into bite-sized pieces.
• Peel, then cut half the onion (whole onion for 4 servings) into 1/4-inch pieces.

• To an unlined baking sheet, add cauliflower and 1 tbsp (2 tbsp) oil.
• Season with half the garlic salt and pepper, then toss to coat.
• Roast in the middle of the oven for 14-16 min, until browned.
• Pat chicken dry with paper towels. Season with salt and pepper.
• Heat a large non-stick pan over medium-high. When hot, add 1/2 tbsp (1 tbsp) oil, then chicken. Sear for 3-4 min per side, until chicken is golden and cooked through.** Transfer to a plate and cover to keep warm.

• Meanwhile, to the boiling water, add rigatoni.
• Cook for 12-13 min, stirring occasionally, until tender but still firm to the bite.
• Reserve 1/2 cup (1 cup) pasta water. Strain rigatoni, then return to the pot, off heat.

• Heat the same pan over medium.
• When hot, add 1 tbsp (2 tbsp) butter, then onions. Cook for 3-4 min, stirring often, until softened.
• Sprinkle flour and remaining garlic salt over onions.
• Cook for 1 min, stirring often, until onions are coated.
• Add cream and 1/2 cup (1 cup) milk, then bring to a boil.
• Once boiling, cook for 1 min, stirring often, until sauce thickens.
• Remove from heat, then add spinach. Stir for 1 min, until wilted.

• To the pot with rigatoni, add cheese, creamy sauce, half the reserved pasta water and cauliflower. 
• Stir for 1 min, until cheese melts. (TIP: For a lighter sauce consistency, add more reserved pasta water, 1-2 tbsp at a time.)
• Season with salt and pepper.

• Thinly slice chicken.
• Divide cheesy creamy cauliflower pasta between bowls.
• Top bowls with chicken.
• Sprinkle chili flakes over top, if you like.

If you've opted to add chicken breast tenders, pat dry with paper towels. Season with salt and pepper. Heat a large non-stick pan over medium-high. When hot, add 1/2 tbsp (1 tbsp) oil, then chicken. Sear for 3-4 min per side, until chicken is golden and cooked through.** Transfer to a plate and cover to keep warm.

Thinly slice chicken. Top bowls with chicken.