Heat oil in a large skillet over medium-high heat and add onion, garlic, cumin, salt and pepper. Sauté for about 1 minute or until onion starts to soften. Make sure the oil is very hot then add in the riced cauliflower and toss the pan to coat in oil. Allow the cauliflower rice to soften and brown, stirring occasionally, about 3 minutes. Stir in beans, cilantro and lime zest and juice. Cook a minute more to warm through and serve.