A big pot of vegetable and lentil stew is warm, filling, and surprisingly low in calories for how hearty it is. Make a batch, eat it all week.
Heat 2 tbsp olive oil in a large Dutch oven or stew pot over medium heat until shimmering but not smoking.
Add the chopped onion, diced carrots, and chopped celery. Sauté for 6–8 minutes, stirring occasionally, until vegetables are softened and onion is translucent.
Stir in minced garlic, dried thyme, oregano, and cumin. Cook for 1 minute until aromatic.
Add the lentils, zucchini, red bell pepper, canned diced tomatoes with juices, and vegetable broth. Increase heat to high and bring the mixture to a boil.
Reduce heat to low, cover, and simmer for 35–40 minutes, stirring occasionally, until lentils are tender but not mushy. Skim any foam if needed.
Stir in the baby spinach during the last 5 minutes of cooking, and season with salt and black pepper to taste.
Taste and adjust seasoning. Serve hot, optionally garnished with fresh herbs.