Start by chopping all of your vegetables. Set them aside, ready for use.
Heat oil in a large saucepan over medium heat. Add the onions and garlic and sauté for 5 minutes or until fragrant.
Add the diced carrots and celery. Sauté for another 10 minutes.
Stir in the lentils, cumin, turmeric, coriander and salt. Cook for 1-2 minutes.
Add the diced tomatoes, coconut milk and broth. Stir together and bring to a boil over high heat.
Reduce heat to medium and let simmer, covered for 30-35 minutes or until the lentils and vegetables are cooked and tender. Stir occasionally.
Once it's done cooking, stir in the spinach and lemon juice. Cook 1-2 minutes until the spinach softens.
Serve immediately or let it cool slightly and store in airtight containers in the fridge for up to 4 days. Let it cool completely before storing in the freezer.