
To cook the quinoa, combine rinsed quinoa and 2 cups of water in a medium saucepan. Bring to a boil over medium-high heat, then reduce to a gentle simmer and cook until the quinoa absorbs the water, about 15 minutes, adjusting the heat as needed. Remove from heat, cover, and let it rest for 5 minutes to fluff up.
While the quinoa cooks, prepare the dressing by whisking together olive oil, lemon juice, garlic, mustard, salt, and red pepper flakes. Add freshly ground black pepper to taste.
To toast the almonds, heat ¼ teaspoon olive oil in a small skillet over medium heat until shimmering. Add the almonds and a pinch of salt, stirring frequently to prevent burning, until they are golden and fragrant. Transfer the toasted almonds to a medium serving bowl to cool.
Once the quinoa is cooked, fluff it with a fork and transfer it to your serving bowl. Drizzle the dressing over the quinoa and toss to combine. Add the chopped sun-dried tomatoes, then let it sit for a few minutes before adding the spinach to prevent wilting. Toss again, adjusting seasoning with additional salt and pepper if needed, and serve immediately.