Preheat your oven to 200°C (400°F). Line a large baking sheet with parchment paper or aluminum foil for easier cleanup. This prevents sticking and makes washing up a breeze.

In a small bowl, prepare the garlic butter sauce. Melt the 30g (2 tbsp) of unsalted butter in a microwave-safe bowl or in a small saucepan over low heat. Add the minced garlic (4 cloves), 15ml (1 tbsp) of lemon juice, 3g (0.5 tsp) of black pepper, and 1g (0.25 tsp) of red pepper flakes (if using). Stir to combine. Set aside.

Place the prepared steak strips (600g or 1.3 lb) and trimmed asparagus pieces (500g or 1 lb) onto the prepared baking sheet. Ensure they are in a single layer, not overcrowding the pan. Overcrowding can lead to steaming instead of roasting, resulting in less desirable texture for both the steak and asparagus.

Drizzle 30ml (2 tbsp) of olive oil over the steak and asparagus. Season generously with 5g (1 tsp) of salt and the remaining 3g (0.5 tsp) of black pepper. Toss everything directly on the baking sheet to ensure an even coating of oil and seasonings.

Arrange the steak strips and asparagus pieces into an even layer on the baking sheet. It's helpful to place the asparagus on one side and the steak on the other, or mix them if preferred, ensuring space between pieces for optimal roasting.

Roast in the preheated oven for 10-12 minutes. The exact time will depend on the thickness of your steak strips and asparagus. For medium-rare steak, aim for the lower end of the time range. For well-done steak, you might need a minute or two longer. The asparagus should be tender-crisp, bright green, and slightly charred.

Remove the baking sheet from the oven. Drizzle the prepared garlic butter sauce evenly over the steak and asparagus. Toss gently on the pan to coat everything.

Return the baking sheet to the oven for an additional 2-3 minutes, or until the garlic butter sauce is melted and fragrant, and the steak is cooked to your desired doneness. This final step infuses the flavors beautifully.

Remove from the oven. Serve immediately. You can garnish with fresh parsley or an extra squeeze of lemon juice if desired.