Preheat your oven to 250C (480F). Layer broccoli on a roasting tray so the florettes aren't touching each other. Drizzle with a little oil. Bake for 10 minutes or until broccoli is defrosted.
Push the hot broccoli together in a single layer. Top with tuna and grated cheese.
Pop back in the oven for another 2-3 minutes or until cheese is melted and golden.
Serve hot in bowls with lemon wedges on the side freshly cracked black pepper and sea salt flakes.