Preheat oven to 200C (400F). Arrange pumpkin on a tray, drizzle with a little olive oil, season with salt and pepper and roast 20-25 minutes or until tender and golden.Meanwhile, bring a large pot of salted water to the boil. Add buckwheat and cook 5-7minutes or until just tender, drain well and transfer to a bowl. Add lemon juice, olive oil and a little salt, to taste. Combine ingredients for the pumpkin seed and pickled chilli pesto in a small food processor and pulse until smooth-ish. Season with salt, to taste.To serve, arrange pumpkin wedges on a platter, scatter over buckwheat, dollop on pumpkinseed + pickled chilli pesto and a little yoghurt and top with sliced pickled chillies.