Cut the leaves and stem from the cauliflower head and discard.
Chop the cauliflower into smaller florets and place them in the food processor. Process until the cauliflower becomes couscous-size pieces: ¼–½ the size of rice.
Heat a skillet with the olive oil to medium heat and sauté the garlic and onion until the onion becomes translucent and slightly tender, about 5 minutes.
Add the cauliflower, black beans, cilantro, lime juice, green onion, salt, pepper and optional dash of cayenne. Stir to coat with oil. Cook for 8 to 10 minutes, stirring occasionally.