Working in batches, pulse cauliflower florets in a food processor until they resemble coarse rice grains, about 8 to 10 pulses. Do not over-process or it will get mushy. Alternatively, grate on the large holes of a box grater. You should have about 6 cups.

Heat 1 tablespoon olive oil in a large skillet over medium-high heat. Add ground beef and cook, breaking it up with a wooden spoon, until no pink remains, about 6 to 7 minutes. Add diced onion and cook until softened and edges turn golden, about 4 minutes. Stir in garlic and cook until fragrant, 30 seconds.

Push beef to one side of the pan. Add tomato paste, smoked paprika, cumin, and red pepper flakes to the empty space. Cook the paste and spices for 1 minute until darkened and fragrant, then stir everything together. Pour in beef broth, scrape up any browned bits, and simmer until slightly thickened, about 2 minutes. Transfer beef mixture to a bowl and set aside.

Wipe out the skillet if needed. Heat remaining 1 tablespoon olive oil over medium-high heat. Add riced cauliflower and salt. Cook, stirring occasionally, until tender but still with some bite, about 5 to 6 minutes. The cauliflower should look mostly dry and have a few golden spots - this prevents a soggy final dish.

Return beef mixture to the skillet with cauliflower rice. Toss everything together and cook for 1 minute to meld flavors. Taste and adjust seasoning. Serve hot, garnished with fresh parsley and Parmesan if desired.