Start by boiling your fettuccine according to the package directions. Make sure it’s al dente because it will continue cooking slightly when mixed with the sauce. Drain and set aside, reserving a little pasta water.
Heat olive oil in a large skillet over medium heat. Add chicken, chili powder, paprika, cumin, garlic powder, salt, and pepper. Cook until the chicken is golden and fully cooked, about 6–8 minutes.
In the same skillet, add sliced bell peppers and onions. Sauté for 5 minutes until tender but still slightly crisp. This keeps their vibrant color and texture.
Lower the heat and pour in heavy cream and chicken broth. Stir to combine and let it simmer for 3–4 minutes. Add Parmesan cheese gradually, stirring until smooth.
Add the cooked pasta to the skillet and toss everything together until evenly coated with the creamy sauce. If the sauce is too thick, add a splash of reserved pasta water.
Sprinkle with crushed red pepper flakes if you like a little heat. Taste and adjust seasoning with salt and pepper. Serve immediately while warm and creamy.