Preheat your oven to 400°F and prepare a grill or grill pan over medium-high heat.
Toss the sliced zucchini and red bell peppers with olive oil, salt, and pepper, then roast on a baking sheet for 15-18 minutes until tender.
While vegetables roast, bring a small pot of water to a boil, carefully lower the egg in, and cook for 6 and a half minutes for a jammy yolk.
Immediately transfer the egg to an ice bath, let cool, then peel and slice in half.
Season the beef sirloin with sea salt and black pepper, then grill for 3-4 minutes per side until your desired doneness is reached.
Let the beef rest for 5 minutes before slicing into thin strips across the grain.
Arrange the roasted vegetables on a plate, top with the grilled beef strips and the soft-boiled egg, and finish with a squeeze of lemon if desired.