Heat oil in a saucepan over medium heat and sauté onion until it just begins to brown, roughly 8 minutes.
Add finely chopped garlic, ginger, curry power and red pepper flakes and cook, stirring, for 2 minutes.
Add lentils, tomatoes, ½ cup cilantro, salt and 2½ cups vegetable broth.
Stir coconut milk thoroughly and add ¾ cup to pot, reserving rest for garnish.
Bring ingredients to a boil then reduce to simmer and cook 20 to 25 minutes, until lentils are soft.
Ladle into bowls and top with fresh cilantro, a drizzle of coconut milk and a squeeze of lime.