Dice the onion and carrots. Mince the garlic.
In a large stockpot over medium-high heat, sauté the onion and carrots for 7–8 minutes until softened. (Use a small amount of water or broth if cooking oil-free.)
Add the garlic, cumin, and smoked paprika. Stir and cook for 1 minute until fragrant.
Add the vegetable broth, diced tomatoes, and lentils. Stir well and bring to a light boil.
Reduce heat, cover, and let simmer for 25–30 minutes, or until lentils are tender.
Roughly chop the spinach and add it to the soup during the last few minutes of cooking.
Stir in apple cider vinegar if using, and season with salt to taste.
Serve warm.
Tips
Rinse lentils well before cooking to remove debris.
Adjust thickness by adding more broth if needed.
Add extra vegetables like celery or bell peppers for variation.
Storage
Refrigerator: Store in an airtight container for up to 4 days.
Freezer: Freeze for up to 3 months.