Peel and dice 1 large carrot and 1 medium onion.
Place 2 cups dried lentils in a strainer then rinse under cool water. Sift through them as you are rinsing and remove any discolored lentils. Set aside to drain.
Heat 2 tablespoons olive oil in a large pot over medium-high heat. Add the carrots and onion and sauté until they become soft, ~5 minutes. Add the garlic, pepper, cumin, paprika and thyme. Stir to combine then cook ~1 minute to allow the flavors to blend.
Add the broth, diced tomatoes with liquid and the lentils. Stir to combine and bring to a soft boil. Cover then reduce the heat. Allow the soup to simmer, stirring occasionally until the liquid starts to thicken, ~30 minutes.
Stir in the chopped spinach and allow to simmer for another 5 minutes.
Remove from heat. Serve immediately, or transfer to an air-tight container and store in the refrigerator. Lentil soup will remain good for ~5 days. You can also freeze it for a future meal