Heat oil in a saucepan over medium-high heat. Add onion and cook, stirring frequently, about 5 minutes. Add carrot and continue cooking for 10 more minutes. Add tomato, garlic, chile pepper, cinnamon stick, lemongrass, and ginger. Cook, stirring occasionally, for 5 more minutes. Stir in curry powder and continue cooking for 5 more minutes.
Remove cinnamon stick and blend the remaining mixture in a food processor until smooth, working carefully as it will be very hot. Return pureed mixture to the saucepan and stir in the water. Bring to a boil over medium-high heat, approximately 5 minutes. Remove from heat and whisk in coconut milk. Add salt and lemon juice to taste.
YIELD: 1 1/2 cups I PREP TIME: 10 min I COOK TIME: 35 min I TOTAL TIME: 45 min