Heat olive oil in a large non-stick skillet over medium heat.
Add the chopped onion and cook for 3 minutes until translucent.
Add the minced garlic and cook for 1 minute until fragrant.
Add the lean ground beef to the skillet. Cook, breaking it apart with a spatula, until browned and cooked through, about 6-8 minutes.
Stir in the diced red bell pepper, zucchini, and sliced mushrooms. Cook for 5 minutes until vegetables are tender.
Add ground cumin, smoked paprika, dried oregano, black pepper, salt, and crushed red pepper flakes. Stir well to combine and cook for 2 more minutes.
In a separate non-stick pan, lightly sauté the cauliflower rice over medium heat for 3-4 minutes until tender but not mushy.
Remove both pans from heat. Stir fresh lemon juice and chopped parsley into the ground beef and vegetable mixture.
Serve the ground beef and vegetable mixture over the cauliflower rice.