Build the base: Heat the olive oil in a large pot or Dutch oven over medium heat. Add the onion, carrots, and celery and cook for 8 to 10 minutes, stirring now and then, until the vegetables are soft and the onion turns golden at the edges. Don't rush this part, it's where the sweetness in the finished bowl comes from.

Bloom the spices: Stir in the garlic, cumin, coriander, smoked paprika, and thyme and cook for 1 minute, until everything smells toasty. Add the tomato paste and cook 1 minute more, stirring, until it darkens from bright red to brick.

Add the lentils and broth: Pour in the diced tomatoes, lentils, broth, bay leaves, salt, and pepper. Scrape the bottom of the pot to lift the browned bits, then bring it to a boil.

Simmer: Reduce the heat to low, cover partially, and simmer for 30 to 35 minutes, until the lentils are tender enough to mash easily against the side of the pot but still hold their shape. Stir once or twice so nothing sticks.

Thicken it: Fish out the bay leaves. Blend about 2 cups of the soup with an immersion blender right in the pot, or scoop 2 cups into a blender, puree until smooth, and stir it back in.

Wilt the kale: Stir in the chopped kale and simmer uncovered for 5 minutes, until it's tender and deep green. Add a splash of water or broth if the pot has gotten thicker than you like.

Finish with lemon: Take the pot off the heat and stir in the lemon juice. Taste and add more salt if it needs it, which it usually does. Ladle into bowls and scatter parsley over the top.