Preheat oven to 180˚C fan-forced and grease and line a large oven tray with baking paper. Place pumpkin on tray, drizzle with oil and season. Bake until golden and cooked (35-40 minutes).
Meanwhile, for paste, place ingredients in a food processor and process.
Heat oil in a large heavy-based saucepan. Add onion and chillies and cook, stirring occasionally, until onion begins to brown (5-6 minutes). Add paste and cook, stirring continuously, until fragrant (3 minutes). Add saffron, two-thirds tomato, coconut milk and coriander root with 2 cups water; bring to the boil and stir to combine. Reduce heat to low, cover with lid ajar, and simmer until reduced by one-quarter (20-25minutes); add lime juice, season to taste and stir to combine.
Remove lid, add prawns and cook, stirring occasionally, until prawns are just cooked (4-5 minutes). Divide pumpkin among serving bowls and spoon over curry with prawns. Scatter with curry leaves, remaining tomato and charred red chillies. Serve with flatbread.