Prep your base: Warm the olive oil in a large pot over medium heat.
Add the onion, carrots, and celery with a pinch of salt. Cook 5–7 minutes, stirring occasionally, until the vegetables soften and the onion turns translucent.
Add aromatics: Stir in the garlic, cumin, smoked paprika, thyme, and bay leaf. Cook 1 minute until fragrant, being careful not to let the garlic brown.
Build the body: Add the lentils, diced tomatoes with their juices, and the vegetable broth.
Stir, scraping the bottom of the pot to lift any browned bits. Bring to a boil.
Simmer until tender: Reduce heat to a gentle simmer. Cover partially and cook 20–25 minutes, stirring occasionally, until the lentils are just tender but not falling apart.
Add quick-cooking veggies: Stir in the zucchini and cook 5–7 minutes more until tender.
If using kale, add it now so it has time to soften; if using spinach, wait until the end.
Finish with brightness: Remove the bay leaf. Stir in the lemon juice and spinach (if using). Taste and season with salt and pepper.
Add red pepper flakes if you want a little heat.
Serve and garnish: Ladle into bowls and top with fresh parsley and a drizzle of olive oil. For a non-vegan option, a sprinkle of Parmesan adds richness.