Preheat your air fryer to 400°F.
Slice the sirloin steak into 1-inch cubes, removing any large pieces of gristle.
In a large mixing bowl, combine the steak cubes and broccoli florets.
Drizzle the avocado oil over the steak and broccoli, then sprinkle with garlic powder, dried rosemary, dried thyme, sea salt, and black pepper.
Toss the mixture thoroughly until the steak and vegetables are evenly coated with the oil and seasonings.
Place the mixture into the air fryer basket in a single layer, working in batches if necessary to avoid overcrowding.
Air fry for 8 to 10 minutes, shaking the basket halfway through, until the steak is browned and the broccoli is tender with charred edges.
While the steak cooks, ensure the cooked quinoa is warmed through in a small saucepan or microwave.
Divide the warm quinoa into serving bowls and top with the air-fried steak and broccoli.
Drizzle the fresh lemon juice over each bowl just before serving for a vibrant finish.