Heat a large soup pot or dutch oven over medium heat. Add olive oil, then the onion.
1 Tablespoon extra virgin olive oil, 1 large yellow onion
Sauté the onion until it is starting to become golden, then add the garlic, salt, and red pepper flakes. Cook for a few minutes more until the garlic begins to brown as well.
3-4 cloves garlic, 1 teaspoon salt, ¼ teaspoon red pepper flakes
Add the celery and carrots, and sauté for about 5 minutes, until the vegetables are slightly softened.
2 medium carrots, 2 large stalks celery
Now add the canned tomatoes with their juices, the vegetable broth, the lentils, and the kale.
1.5 cups lentils, 2 14 oz cans diced tomatoes, 6 cups vegetable broth, 1 bunch Lacinato kale
Bring the soup to a boil, then reduce the heat to low and cover. Simmer until the lentils are tender, about 20-30 minutes.
Taste and decide whether you need a bit of salt and pepper, and season as you like. Let the soup meld together for a few minutes more, then you're ready to serve.
salt and pepper