Preheat the oven to 220 C (425 F). Toss diced sweet potatoes with 15 ml (1 tbsp) olive oil, 1/2 tsp salt, 1/2 tsp cumin, and a pinch of black pepper. Spread in a single layer on a sheet pan. Roast 20-25 minutes until edges are golden and centers tender, flipping once for even caramelization.
While sweet potatoes roast, rinse 250 g (1 cup) quinoa under cold water until rinse runs clear. Combine quinoa with 480 ml (2 cups) water and a pinch of salt in a medium saucepan. Bring to a boil, lower heat, cover, and simmer 12-15 minutes until water is absorbed. Remove lid and fluff with a fork; steam 5 minutes off heat for extra fluffiness.
Make the dressing by whisking 30 ml (2 tbsp) lemon juice, 15 ml (1 tbsp) maple syrup, 15 ml (1 tbsp) olive oil, 1/4 tsp salt, and 1/8 tsp black pepper until emulsified. Taste and adjust acid or sweetness for balance.
In a large mixing bowl, combine the cooked quinoa, roasted sweet potatoes, 60 g (1/2 cup) chopped red onion, 60 g (1/2 cup) chopped parsley or cilantro, and 30 g (1/4 cup) toasted pumpkin seeds. Pour the dressing over and gently toss to coat, taking care not to mash the sweet potatoes.
Serve warm or at room temperature. Garnish with extra herbs, a squeeze of lemon, and a sprinkle of flaky salt for bright finishing notes. Leftovers taste even better after a few hours as flavors meld.