Preheat the oven to 220°C (430°F) or 200°C (fan-forced). Line a baking tray with parchment paper. Peel, deseed, and chop the pumpkin into cubes approximately 3 cm (1.2 inches) in size. Expect to yield around 1 kg of usable pumpkin.
In a mixing bowl, combine the cubed pumpkin with olive oil, minced garlic, salt, and pepper. Use a rubber spatula to coat the pieces evenly. Distribute the seasoned pumpkin across the lined tray in a single layer.
Roast in the oven for 20 minutes, then use tongs or a spatula to turn the pieces. Continue roasting for an additional 7–10 minutes, until the pumpkin is golden and tender yet still holds its shape.
In a small bowl, mix the yogurt, lemon juice, olive oil, salt, pepper, and minced garlic. Let the sauce rest for at least 10 minutes to allow the flavors to meld.
Heat a dry skillet over medium-high heat. Toast the pine nuts by stirring frequently until they emit a nutty aroma and are lightly browned on both sides. Remove from heat immediately to prevent burning.
To assemble, arrange the roasted pumpkin in a mound on a serving plate. Drizzle with the lemon yogurt sauce, add a touch more olive oil if desired, and scatter the toasted pine nuts, sumac, and chopped herbs on top.
This dish shines when served warm or hot but is equally enjoyable at room temperature on a warm day. If serving later, cool the roasted pumpkin completely before garnishing just prior to serving.