Preheat oven to 400°F. Spread cauliflower florets in a single layer on a parchment-lined baking sheet. Lightly spray with cooking spray. Roast for 30 minutes. Let cool slightly, then transfer to a food processor or blender. Add 1 cup of chicken broth and process until smooth. Transfer to a bowl, season with salt and pepper, and set aside.

Heat the ground beef in a large skillet over medium-high heat until browned. Drain the beef on paper towels.

Add the diced onion, minced garlic, and diced bell peppers to the same skillet over medium-high heat. Cook, stirring frequently, for about 3 minutes. Stir in the cumin and paprika and cook for 1 minute more, stirring constantly. Return the browned beef to the skillet. Stir in the remaining 1 cup of chicken broth, diced tomatoes, chopped olives, and balsamic vinegar. Cook for 6 minutes, or until the mixture has thickened slightly and reduced by half. Season with salt and pepper. Transfer the beef mixture to an 8 or 9-inch square baking dish, spreading it out evenly.

Spoon the mashed cauliflower topping evenly over the beef mixture.

Cover the dish with foil and bake for 20 minutes at 400°F. Remove the foil and bake for an additional 10 minutes. Serve hot.