Season the chicken. Pat the chicken dry, then season with 1/2 teaspoon salt, 1/4 teaspoon black pepper, and Italian seasoning. This helps build flavor from the start.
Sear the chicken. Heat the olive oil in a large skillet over medium-high.
Add the chicken in a single layer and cook 5 to 7 minutes, stirring once or twice, until golden and cooked through. Transfer to a plate and tent loosely with foil.
Soften the aromatics. Lower heat to medium. Add the butter to the same skillet.
Stir in the onion with a pinch of salt and cook 3 to 4 minutes until soft. Add the garlic and red pepper flakes, and cook 30 seconds until fragrant.
Cook the cauliflower rice. Add the cauliflower rice and a good pinch of salt. If using frozen, break up any clumps.
Cook 4 to 6 minutes, stirring often, until the rice is tender and most moisture has evaporated. You want a slight bite, not mush.
Bring it together. Pour in the chicken broth and let it simmer 1 minute to loosen any browned bits. Stir in the Parmesan until it melts and lightly coats the rice.
If it looks dry, add another splash of broth.
Finish with brightness. Stir in the lemon zest, lemon juice, and parsley. Return the chicken and any juices to the skillet and toss to combine. Taste and adjust with salt, pepper, or more lemon as needed.
Optional veggies. If adding spinach or peas, fold them in during the last minute of cooking until wilted or warmed through.
Serve. Spoon into bowls and finish with extra Parmesan and a crack of black pepper.