Bring 4 liters of water to a rolling boil with 10g of salt.
Cook pasta until al dente, approximately 10 to 12 minutes.
Season steak strips with salt and black pepper.
Heat 30ml olive oil in a heavy-bottomed skillet over high heat until it reaches smoking point.
Sear steak strips in batches for 2 minutes per side until browned; remove and set aside.
Add remaining 30ml olive oil to the same skillet over medium-high heat.
Sauté bell peppers and red onion for 6 minutes until edges are charred and vegetables are tender-crisp.
Incorporate minced garlic and red pepper flakes, sautéing for 60 seconds until fragrant.
Deglaze the skillet with 60ml of reserved pasta cooking water, scraping the fond from the bottom.
Combine drained pasta and seared steak with the vegetables in the skillet.
Toss vigorously over medium heat for 2 minutes to emulsify the sauce.
Garnish with grated Parmesan and chopped parsley before service.