Heat 2 tablespoons olive oil in a large pot over medium heat. Add 1 large chopped onion, 3 peeled and chopped carrots, 3 chopped celery ribs, and a pinch of salt. Sauté, stirring occasionally, for 6–8 minutes until the onions are soft and translucent.
Stir in 5 minced garlic cloves and 1/2 teaspoon dried thyme. Cook for 1 minute, until fragrant.
Add 1 can diced tomatoes (28 ounces) and stir. Cook for 2 minutes to combine flavors.
Add 1 cup rinsed quinoa, 6 cups low-sodium vegetable broth, 2 bay leaves, and 1/4 teaspoon red pepper flakes (if using). Stir, increase heat to bring the mixture to a boil.
Once boiling, reduce heat to a simmer and cook for 25 minutes, until the quinoa is tender.
Add 1 can white beans (15 ounces), drained, and 1 1/2 cups chopped kale. Simmer for 5 more minutes, until the kale is tender and the beans are heated through.
Remove and discard the bay leaves. Stir in 2 teaspoons lemon juice and season with salt and pepper to taste.
Ladle the soup into bowls and garnish with chopped fresh herbs, if desired. Serve hot.