01 - Preheat the oven to 400°F. Line a baking tray with parchment paper.
02 - Toss pumpkin cubes with olive oil, salt, and pepper. Spread evenly on the tray and roast for 25 minutes or until golden and tender. Set aside to cool slightly.
03 - Reduce oven temperature to 350°F.
04 - Roll out the shortcrust pastry and line a 9-inch tart tin. Trim excess pastry, prick base with a fork, line with parchment paper, and fill with baking beans. Blind bake for 10 minutes, remove beans and parchment, then bake an additional 5 minutes until lightly golden.
05 - In a skillet, heat a little olive oil over medium heat. Sauté red onion and garlic until softened, approximately 4 minutes. Remove from heat and allow to cool.
06 - Whisk together eggs, crème fraîche or cream, thyme, nutmeg, salt, and pepper in a large bowl. Fold in the cooled sautéed onion and garlic.
07 - Arrange the roasted pumpkin evenly over the pastry base. Scatter crumbled feta cheese on top, then pour the egg mixture over everything.
08 - Sprinkle pumpkin seeds over the filling if desired.
09 - Bake for 25 to 30 minutes until the filling is set and lightly golden.
10 - Allow the tart to cool slightly before garnishing with fresh thyme sprigs. Serve warm or at room temperature.