Place the cauliflower in a food processor and pulse a few times, until it resembles grains of rice. Heat the olive oil in a skillet over medium heat. Add the cauliflower rice and cook until tender, about 4-5 minutes. Set aside.
In a small bowl, mix the chili powder, cumin, paprika, garlic powder, onion powder, salt, and cayenne. Set aside.
Place ground beef in a large nonstick skillet over medium heat. Cook, stirring to break up clumps, until the beef is browned, about 8-10 minutes. Drain off most of the excess fat, but leave a little to help the spices blend with the meat. Sprinkle in the spice blend and cook until mixed thoroughly, about another 1-2 minutes.
Divide the cauliflower rice and beef evenly among four bowls. Add 5 halved cherry tomatoes, 1/2 cup lettuce, 1/4 cup cheddar cheese, and 1 tablespoon guacamole to each bowl. Serve immediately.