Preheat your oven to 425°F (220°C). Arrange the cauliflower florets on a baking sheet, drizzle with 1 tablespoon of olive oil, and season with salt and pepper. Roast for 20-25 minutes until lightly browned and tender.
On a separate baking sheet, place the red bell pepper halves skin-side up. Roast alongside the cauliflower until the skin is charred, about 15-20 minutes. Remove from the oven, cover with foil or a bowl for 10 minutes to steam, then peel off the skin and chop the pepper.
While the vegetables are roasting, heat the remaining olive oil in a large pot over medium heat. Add the diced onion and garlic, sautéing until translucent and fragrant, about 5 minutes.
Increase the heat to medium-high and add the ground beef to the pot. Cook, breaking it apart with a spoon, until browned and cooked through.
Stir in the diced tomatoes, tomato paste, beef broth, chili powder, cumin, paprika, and cayenne pepper. Bring the mixture to a simmer.
Add the roasted cauliflower and red pepper to the pot. Stir well to combine.
Reduce the heat to maintain a gentle simmer. Cook for an additional 15 minutes, allowing the flavors to meld.
Taste and adjust seasoning with additional salt and pepper if necessary.
Serve hot with optional toppings like shredded cheese, sour cream, or chopped chives.