Heat the coconut oil in a large pot over medium heat. Add the diced onion and cook for 4 minutes until it softens.
Stir in the minced garlic, ginger, and Thai red curry paste. Cook for 1 minute until the paste smells fragrant.
Add the rinsed red lentils, diced sweet potatoes, vegetable broth, and salt. Bring the mixture to a boil.
Reduce the heat to low, cover the pot, and simmer for 20 minutes, stirring once or twice so the lentils do not stick.
Pour in the coconut milk and continue to simmer uncovered for 10 more minutes until the sweet potatoes are tender and the stew thickens.
Remove the pot from the heat and stir in the lime juice. Taste and adjust salt if needed.
Ladle the stew into bowls and top each serving with chopped cilantro.