Place the olive oil into a large, 6-quart Dutch oven set over medium heat. Once hot, add the onion, carrot, celery, and salt, and sweat until the onions are translucent, 6 to 7 minutes.
Add the lentils, tomatoes, broth, coriander, cumin, and grains of paradise, and stir to combine.
Increase heat to high and bring just to a boil. Reduce the heat to low, cover, and cook at a low simmer until the lentils are tender, 35 to 40 minutes.
Using an immersion blender, puree to your preferred consistency. Serve immediately.