Creating Sizzling Chinese Pepper Steak with Onions is straightforward when you follow these simple steps:

1. Marinate the Beef: In a bowl, combine the sliced flank steak with soy sauce, oyster sauce, cornstarch, black pepper, and sugar. Allow the mixture to marinate for about 10-15 minutes.
2. Prepare the Vegetables: While the beef is marinating, slice the onion and bell peppers. Mince the garlic and ginger so they are ready for cooking.
3. Heat the Pan: In a large skillet or wok, heat 2 tablespoons of vegetable oil over medium-high heat until it shimmers.
4. Stir-Fry the Beef: Add the marinated beef to the hot pan in a single layer. Stir-fry for 2-3 minutes until browned but not fully cooked. Remove from the pan and set aside.
5. Sauté the Vegetables: In the same pan, add the sliced onions and bell peppers. Stir-fry for about 3-4 minutes until they begin to soften. Add the garlic and ginger, stir-frying for an additional minute.
6. Combine Ingredients: Return the cooked beef to the pan. Mix everything together and stir-fry for another 2-3 minutes until the beef is cooked through and the vegetables are tender-crisp. Season with salt to taste.
7. Serve Hot: Transfer the sizzling pepper steak to a hot plate for serving. Garnish with chopped green onions for a fresh touch.

These steps will guide you through the preparation of this incredible dish, ensuring each element shines through.