Thickly slice the capsicum. Finely chop the celery. Crush or finely chop the garlic. Thinly slice the spring onion. Preheat the grill to high.
Step 2 — Cook vegetables
Heat 2 tsp olive oil in a medium ovenproof frypan over medium-high heat (see cooking tip). Cook the capsicum and celery, stirring regularly, for 4 mins or until softened. Add half the garlic, a pinch of dried oregano and season with salt and pepper. Cook, stirring, for 20 secs or until fragrant.
Step 3 — Make tomato sauce
Add the tomatoes to the vegetables and bring to a simmer. Reduce the heat to medium and cook, stirring occasionally, for 8 mins or until slightly thickened. Stir in ½ tsp sugar. Taste, then season with salt and pepper.
Step 4 — Make garlic butter
Meanwhile, put the remaining garlic, a large pinch of dried oregano* and 20g butter in a small frypan over medium heat. Cook, swirling the pan occasionally, for 1 min or until the butter is melted and fragrant. Remove from the heat, then season with salt and pepper.
Step 5 — Grill prawn saganaki
Season the prawns with salt and pepper. Push the prawns into the tomato sauce, then crumble over the feta. Grill for 8 mins or until the prawns are cooked through and the feta is melted.
Step 6 — Warm flatbread
While the prawn saganaki is grilling, put the tortillas, slightly overlapping, on a large oven tray. Drizzle with the garlic butter, spreading with the back of a spoon to cover. Warm the tortillas by putting on the oven shelf, below the prawn saganaki, for 6-8 mins until heated through. Scatter the prawn saganaki with the spring onion and serve at the table with the flatbread.