Bring a large pot of water to a boil under a steamer basket. Place the cauliflower florets in the steamer basket and cook for 10 to 12 minutes, or until soft.
In a skillet over medium heat, add half of the avocado oil and the onion. Cook for 5 to 7 minutes, until cooked through, then lower the heat to low and add the garlic. Cook for 1 to 2 minutes more. Set aside.
In a blender, add the steamed cauliflower, onion, garlic, nutritional yeast, coconut milk, lemon juice and 3/4 of the sea salt. Blend on high until smooth and creamy. Set aside.
Season the chicken breast with rosemary, garlic powder and the remaining sea salt. In a skillet over medium heat, add the remaining avocado oil. Then, add the chicken breast and cook for 8 minutes per side. Remove, let it rest for 2 to 3 minutes and then slice.
Plate the zucchini noodles and top with sliced chicken and cauliflower alfredo sauce. Enjoy!