Cook the brown rice according to package directions, or remove frozen cauliflower rice from the freezer to begin thawing if using the lower-carb option.
Preheat the oven to 375°F (190°C).
Prepare the zucchini: for round (ball) zucchini, trim the stem end so the zucchini sits flat and use a pointed teaspoon or melon baller to scoop out the center, leaving a 1/2-inch thick shell; for long zucchini, trim the ends, cut in half lengthwise, and scoop out a shallow boat, leaving about 1/2 inch of flesh.
Microwave the hollowed zucchini for 3–4 minutes on high to soften slightly, then set aside.
Heat 1 teaspoon olive oil in a nonstick frying pan over medium heat, then sauté the chopped onion and red bell pepper about 3 minutes until slightly softened. If using thawing cauliflower rice, add it now and cook with the vegetables.
Add the Spike Seasoning, garlic puree, and ground fennel seed to the vegetables and cook 1–2 minutes more, then transfer the vegetables to a large mixing bowl.
Add the remaining 1 teaspoon olive oil to the hot pan, add the ground beef, and cook over medium-high heat until browned, breaking it up with a turner; then transfer the cooked beef to the mixing bowl with the vegetables.
Stir the cooked brown rice (or thawed cauliflower rice), chopped basil, 1/2 cup of the grated Parmesan, and the chicken stock into the meat and vegetable mixture until evenly combined.
Lightly oil or spray a roasting pan with sides tall enough to hold the zucchini. Pack the stuffing mixture into each zucchini, mounding it as needed, and place the stuffed zucchini close together in the pan so they support one another.
Roast uncovered for 15 minutes, then sprinkle the tops with the remaining Parmesan cheese and return to the oven.
Roast 10–15 minutes more, until the zucchini are tender-crisp and the filling is hot and lightly browned.
Serve the stuffed zucchini hot.