Finely chop the cauliflower into small pieces.
Dice the onion and carrot.
Heat olive oil in a pan and sauté the onion and carrot.
Add tuna and continue to stir-fry together.
Add cauliflower and brown rice, and stir-fry all together.
Season with soy sauce, salt, and pepper to taste.
Once all ingredients are well mixed, the dish is ready.