Heat the oil in a medium saucepan over medium heat.
Add the onion, garlic, ½ teaspoon salt, and ¼ teaspoon pepper and cook, stirring, until soft, 3 to 5 minutes. Add the curry powder and cook, stirring, until fragrant, about 30 seconds more. Add the tomatoes (with their juices) and ½ cup water and bring to a boil.
In a blender, puree until smooth. Top with the yogurt and cilantro.