Heat the vegetable oil in a large pot over medium heat. Add the chopped onion and sauté until translucent, about 5 minutes.
Stir in the minced garlic and grated ginger, cooking for an additional 2 minutes until fragrant.
Add the diced carrot, celery, and potato to the pot, stirring occasionally for about 5 minutes.
Incorporate the shredded chicken (or vegetarian alternative), curry powder, ground cumin, turmeric, salt, and black pepper. Cook for 2-3 minutes to toast the spices.
Pour in the diced tomatoes and chicken or vegetable broth. Bring to a boil.
Stir in the rinsed red lentils. Reduce the heat to low, cover, and simmer for 25-30 minutes until the vegetables are tender and lentils are cooked.
Once cooked, add the coconut milk and lemon juice. Stir well and let it simmer for an additional 5 minutes to combine the flavors.
Taste and adjust seasoning if necessary. Serve hot, garnished with fresh cilantro.