Prep the steak: For easier slicing, chill steak in the freezer for 20–30 minutes.
Slice thinly against the grain. Pat dry with paper towels and season with half the salt and pepper.
Cook the cauliflower rice: Heat a large skillet over medium heat with 1 teaspoon olive oil and the butter. Add cauliflower rice, a pinch of salt, and cook 5–7 minutes until tender and steamy.
Transfer to bowls and keep warm.
Sauté the veggies: In the same skillet, add 1 tablespoon olive oil. Add onions and peppers with a pinch of salt. Cook over medium-high heat, stirring occasionally, until softened and lightly caramelized, 8–10 minutes.
Stir in garlic for 30 seconds. Transfer veggies to a plate.
Sear the steak: Return skillet to high heat. Add remaining oil.
Spread steak in an even layer. Let it sear undisturbed for 1–2 minutes, then stir and cook until just browned, 2–3 minutes more. Don’t overcook.
Deglaze and season: Add Worcestershire (if using) and beef broth.
Scrape up browned bits. Reduce for 1 minute until slightly saucy. Taste and adjust salt and pepper.
Add red pepper flakes if you like heat.
Combine and melt: Return peppers and onions to the pan with the steak. Toss to combine. Lay provolone slices over the mixture, cover the pan for 1–2 minutes, and let the cheese melt into the filling.
Assemble the bowls: Spoon cheesy steak and veggies over cauliflower rice.
Garnish with chopped parsley. Serve hot.