Arrange the rack in the middle of the oven, then preheat the fan-assisted oven to 210 °C / 410 °F or the conventional oven to 220 °C / 430 °F. Line a baking sheet with parchment paper.
Add quinoa to a fine-mash sieve and rinse under running water. Transfer to a saucepan and add water and salt. Place over medium heat, bring to a boil, then cover with a lid and simmer for 12 - 15 minutes.
Peel the sweet potato and cut it into 2 cm x 2 cm (1-inch x 1-inch) cubes. Place on the prepared baking sheet and season with olive oil and thyme. Season with salt and pepper and arrange in a single layer. Place in the preheated oven and roast for 15 - 20 minutes in the fan-assisted oven set to 210 °C / 410 °F or in the conventional oven set to 220 °C / 430 °F or until soft and cooked.
Pour one liter (4 cups) of water into a pot. Season with salt and bring to a boil over high heat. Add the kale and cook for 30 seconds, then immediately drain and cool under cold running water to stop the cooking process.
Stir together the maple syrup, olive oil, grated garlic, and lemon juice in a small bowl. Season with salt and pepper and set aside until needed.
Kale Quinoa Salad
Combine the cooked quinoa, baked sweet potato, kale, grapefruit, thinly sliced red onion, and dressing in a large bowl. Toss to combine until all the ingredients are combined. Serve as a side or main dish.