Finely chop the onion, the garlic, and the ginger.
Heat some oil in a large pot and cook the onion, garlic, and ginger for about 3 minutes on medium heat. Stir frequently.
Then, add the spices and cook for another minute until fragrant. Next, add the tomato paste and stir well. Cook for another 2 minutes.
Then add the red lentils, the diced tomatoes, the coconut milk, and the vegetable broth.
Turn the heat down to low and cook for 25 minutes (without a lid). If the soup is too thick, add more vegetable broth until you reach your desired consistency. Add the lemon juice and season with salt and pepper.
Serve immediately and sprinkle with freshly chopped cilantro and green onion. If you want, you could also add a bit of red pepper flakes on top for a bit of heat. I like to serve my red lentil soup with crusty bread.
Notes
For a lighter version, you can replace the full-fat coconut milk with light coconut milk.
The soup is pretty thick. If you want it to be thiner, add more vegetable broth.
For extra heat, add red pepper flakes to your personal liking.
Stored in an airtight container in the fridge, it will last up to 4 days.