Heat olive oil in a large pot or Dutch oven over medium heat. Add the diced onion and cook for 5 minutes until softened and translucent.

Add the minced garlic and grated ginger to the pot. Cook for 1-2 minutes until fragrant, stirring constantly to prevent burning.

Add the diced carrots and celery to the pot. Cook for 5-7 minutes, stirring occasionally, until the vegetables begin to soften.

Stir in the turmeric, cumin, coriander, and cayenne pepper. Cook for 1 minute until the spices are fragrant and well combined with the vegetables.

Add the cubed sweet potatoes, rinsed red lentils, diced tomatoes, vegetable broth, and bay leaves to the pot. Stir well to combine all ingredients.

Bring the stew to a boil over high heat, then reduce heat to low and simmer for 25-30 minutes, stirring occasionally, until the lentils are tender and the sweet potatoes are fork-tender.

Stir in the coconut milk and simmer for an additional 5 minutes. Season with salt and black pepper to taste.

Remove the bay leaves from the stew. Add the fresh spinach and stir until wilted, about 2 minutes.

Remove from heat and stir in the chopped fresh cilantro. Taste and adjust seasoning if needed.

Serve hot in bowls, garnished with additional cilantro if desired. The stew can be stored in the refrigerator for up to 4 days or frozen for up to 3 months.