Heat two tablespoons of olive oil in a large pot or Dutch oven set over medium heat.
Add the onion, celery, carrots, and bell pepper along with a ½ teaspoon of kosher salt. Cook for about 5-7 minutes, stirring frequently, until the onions are translucent.
Add the zucchini and garlic, and cook for another 2-3 minutes until the garlic is fragrant and the zucchini starts to soften.
Add the crushed tomatoes and chicken broth. Turn heat to medium-high and bring the soup to a boil. Then reduce the heat to medium-low, and let the soup simmer, partially covered, for about 20 minutes.
Turn off the heat and add the kale. Stir until the kale is wilted. Season with salt and pepper to taste.
Notes
If you want to cut the carbs more, reduce the amount of carrots used in the recipe.