In a large skillet over medium heat, saute diced onion in olive oil until tender (about 5 minutes).
Increase heat to medium-high. Add frozen riced cauliflower, tomato paste, tomatoes, cumin, chili powder, garlic, salt and pepper. Continue to cook for about 6-8 minutes, until the cauliflower is light and fluffy and the mixture is hot.
Serve warm.
Notes
This cauliflower rice will last about 3-5 days in an airtight container in the refrigerator.