Heat the olive oil in a Dutch oven over medium high heat until the oil shimmers. Add the carrots and onions and cook for 5 minutes, stirring occasionally. Add the garlic and saute for one minute, stirring constantly.
Add all the spices and cook for another minute, stirring constantly. This is called blooming, and will intensify the flavor of the spices.
Pour in ½ cup of broth to deglaze the pot by scraping the brown bits off the bottom of the pot with a wooden turner.
Pour in 4½ cups of broth, the cubed sweet potatoes, rinsed lentils, and diced tomatoes and mix until well combined.
Cover and bring to a boil over medium-high heat. Turn the heat down to low and simmer for 45 minutes with the lid on, stirring occasionally to prevent the stew from burning.
In the last 10 minutes of cooking, add 1-2 cups of vegetable broth to thin the stew.
During the last 5 minutes, slowly stir until all the spinach until it is wilted.
Remove from the heat. Mix in ½ cup of chopped cilantro and the freshly squeezed lemon juice to brighten the flavors. Taste and adjust seasonings, if necessary. (We added ½ teaspoon of salt.)
Serve warm. Garnish each bowl of soup with the other ½ cup of chopped cilantro.