Place a dutch oven or large saucepan over medium-high heat. Add oil.
Add onion and saute until transluscent, about 5 minutes. Stire in curry paste and cook for 1 minute, stirring constantly. Pour in coconut milk. Rinse the can out with 1/2 cup water and add to pot.
Stir in lentils, cover and bring the curry to a simmer. Reduce heat to medium-low and cook for 10 minutes. Stir in broccoli and cook for 5 minutes, until florets are tender.
Stir in lime juice, pinch of sugar, and season with salt and pepper.
Serve over steamed rice.