Prep the steak: Pat the steak cubes dry with paper towels. Dry surfaces brown better.
Toss with 1 tablespoon olive oil, salt, pepper, and smoked paprika if using. Let sit at room temperature for 10–15 minutes while you prep the broccoli.
Heat the pan: Use a large heavy skillet (cast iron is ideal). Heat over medium-high until hot.
If you flick a drop of water and it sizzles immediately, you’re ready.
Cook the broccoli: Add 1 tablespoon olive oil to the pan. Add broccoli and a pinch of salt. Sauté 4–5 minutes, stirring occasionally, until bright green and crisp-tender with a little char.
Transfer to a plate and keep warm.
Sear the steak bites: Add half the steak cubes to the hot, dry pan in a single layer. Don’t crowd. Sear 1–2 minutes per side until browned on at least two sides and medium-rare to medium inside.
Transfer to a plate and repeat with the remaining steak.
Make the garlic butter: Reduce heat to medium-low. Add butter to the pan. When melted and foamy, stir in garlic and red pepper flakes.
Cook 30–45 seconds, just until fragrant. Do not brown the garlic.
Toss it together: Return steak and broccoli (plus any juices) to the pan. Add lemon juice and parsley.
Toss to coat everything in the garlic butter. Taste and adjust salt and pepper.
Serve: Plate immediately. Finish with an extra squeeze of lemon and a sprinkle of parsley for freshness.