If using fresh, not frozen, cauliflower - remove core, leaves, & any dark spots. Make sure cauliflower is completely dry, coarse chop.
Place chopped cauliflower in food processor (may have to do in multiple batches). Pulse until it is small rice-like texture. Be careful not to go too far or it will be mushy
Heat 2tsp oil in large pan over med-high. Add cauliflower rice + frozen spinach & cook for 6-8min or until heated through. Season w/ S&P.