Bring a large pot of salted water to a boil. Add the rotini pasta and cook according to package instructions until al dente, typically about 8-10 minutes. Drain and set aside.

In a medium bowl, toss the chicken pieces with Cajun seasoning until evenly coated.

In a large skillet over medium-high heat, add 2 tablespoons of olive oil. Once hot, add the seasoned chicken. Cook for about 5-7 minutes, stirring occasionally until the chicken is golden brown and cooked through. Remove the chicken from the skillet and set it aside.

In the same skillet, reduce the heat to medium and add the remaining tablespoon of olive oil. Add the minced garlic and sauté until fragrant, about 1 minute.

Pour in the heavy cream, stirring continuously. Allow it to simmer gently for about 2-3 minutes until it thickens slightly.

Lower the heat and add the shredded cheddar cheese, stirring until melted and smooth. Season with salt, pepper, and crushed red pepper flakes (if using).

Return the cooked chicken to the skillet, alongside the diced bell peppers and spinach. Stir well to combine and let everything heat through for about 2-3 minutes.

Add the drained rotini to the skillet, tossing everything together until the pasta is fully coated with the creamy sauce.

Garnish with sliced green onions on top. Serve warm and enjoy!