Place the olive oil into a large saucepan or Dutch oven and set over medium heat. Add the onions, carrots, celery, and salt, and sweat until the onions are translucent, approximately 6 to 7 minutes.

Add the lentils, tomatoes, broth, coriander, cumin, and curry powder and stir to combine. Increase the 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, approximately 35 to 40 minutes.

Using a stick blender, puree to your preferred consistency. (I like to leave my soup a little bit chunky and even remove a ladle or two of soup and then puree the soup, adding back the reserved soup.) 

Serve immediately.