Rinse the rice until the water runs clear. Put in a small saucepan with 250ml (1 cup) water, cover and bring to a simmer over medium heat. Reduce the heat to low and cook for 12 mins or until tender and the water is absorbed. Turn off the heat and stand, covered, for at least 5 mins.
Step 2 — Prep vegetables
Meanwhile, thinly slice the brown onion. Halve the zucchini lengthwise, then thinly slice. Cut the capsicum into 1.5cm-thick strips. Crush or finely chop the garlic. Thinly slice the spring onion.
Step 3 — Make sauce
Combine the sweet chilli sauce, sriracha sauce, rice wine vinegar, 2 tsp soy sauce and 1 tbs water in a bowl.
Step 4 — Stir-fry beef
Separate the beef stir-fry. Heat 2 tsp oil in a large deep frypan over high heat until very hot (beef stir-fry is best with hot, fast cooking; get the pan very hot before adding the beef and stick to the short cooking time). Stir-fry the beef for 1-2 mins until browned. Remove from the pan.
Step 5 — Stir-fry vegetables
Add 2 tsp oil to the same pan and reduce the heat to medium-high. Stir-fry the brown onion, zucchini and capsicum for 3-4 mins until slightly softened. Add the garlic and stir-fry for 1 min or until fragrant.
Step 6 — Finish stir-fry
Add the sauce, beef and any resting juices to the vegetables. Cook, stirring, for a further 1 min or until combined. Fluff the rice with a fork. Divide the rice and beef mixture among bowls. Scatter over the spring onion to serve.