01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper.
02 - Toss the halved radishes and sliced red onion with 1 tablespoon olive oil, season with salt and pepper, and spread on the baking sheet. Roast for 20-25 minutes until tender and lightly caramelized.
03 - While the vegetables roast, combine quinoa and broth (or water) in a medium saucepan. Bring to a boil, then reduce heat, cover, and simmer for 15 minutes or until liquid is absorbed. Remove from heat and let stand, covered, for 5 minutes. Fluff with a fork.
04 - In a small bowl, whisk together remaining olive oil, lemon juice, Dijon mustard, garlic, parsley, salt, and pepper to make the dressing.
05 - In a large bowl, combine warm quinoa, roasted radishes and onions, baby spinach, and half the feta. Drizzle with dressing and gently toss to combine.
06 - Transfer salad to a serving platter or bowls. Top with remaining feta and toasted nuts, if using. Serve warm.