Rinse the rice and simmer it in 200 ml (3/4 cup plus 1 tbsp) of water: bring to a boil over high heat, cover, turn to low for 15 minutes, then rest 5 minutes.
Heat a large skillet over medium-high heat for 1 minute. No oil is needed for the beef.
Add the beef and onion and break the meat up with a wooden spoon. Cook, stirring, until no pink remains and the beef reaches 71°C (160°F), about 7 minutes.
Add the red pepper, chili powder, cumin, smoked paprika, oregano, salt and diced tomatoes. Reduce the heat to medium and simmer, stirring now and then, until thick and saucy, about 6 minutes.
In another skillet over medium-high heat, cook the riced cauliflower with a pinch of salt, stirring, until tender and any liquid has evaporated, about 5 minutes. Stir in the cooked rice and lime juice.
Divide the rice mixture between four bowls and top with the beef, shredded lettuce, salsa and Greek yogurt.
Tips
Extra-lean beef barely releases fat, so there is nothing to drain.
Swaps
Dairy-free: skip the yogurt.
Bulking: use all rice instead of the cauliflower blend.
Storing and reheating
Keeps 4 days; add the lettuce, salsa and yogurt when serving.