Preheat oven to 400°F (200°C). Rub chicken with olive oil, cumin, salt, and pepper; place in a baking dish.
Spoon salsa verde over chicken, covering each piece. Bake 20–25 minutes until internal temp reaches 165°F (74°C).
Meanwhile, sauté onion in a large skillet over medium heat until soft, 4–5 minutes. Add garlic; cook 30 seconds.
Add riced cauliflower and broth; cook 5–7 minutes until tender. Stir in cilantro and adjust salt.
Let chicken rest 5 minutes, then slice and serve over cauliflower rice with lime and avocado if using.