Prepare the black beans: bring a medium saucepan to medium-low heat. Add oil onions and garlic, and begin to sautee gently until vegetables begin to just sizzle about 1 minute.
Add in celery and pepper, and stir gently prevent rapid burning. When vegetables are aromatic, add in cumin and stir to combine.
Add in black beans water, cilantro, and bay leaf, and bring to a simmer. Reduce heat to low, cover and allow flavors to blend about 15 minutes.
When black beans are finished, remove from heat. Remove bay leaf and season to taste. Keep warm until ready to serve.
Prepare cauliflower taco filling: bring a sautee pan to medium-high heat. Add oil onions and minced garlic, and begin to sweat gently until vegetables are translucent.
Add cauliflower to the pan and fold to incorporate. Pour water/vegetable stock over cauliflower. Reduce heat to medium-low, and cover to steam until cauliflower is tender.
After steaming, gently fold taco seasoning, into cauliflower mixture. Adjust salt to taste. Remove from heat and serve immediately.
For assembly: divide cooked white rice into bowls and top with cauliflower and black beans. Add desired toppings, such as salsa, lime, pepitas, cilantro, etc. Serve immediately.