To prepare salsa, combine the first 4 ingredients; cover and chill.
To prepare soup, combine broth, lentils, and onion in a Dutch oven over medium-high heat; bring to a boil. Cover, reduce heat, and simmer 15 minutes or until lentils are tender. Pour half of lentil mixture in a blender; let stand 5 minutes. Process until smooth. Pour pureed lentil mixture into a bowl. Pour remaining lentil mixture into blender; process until smooth. Add coconut milk, tomato paste, ginger, cumin, and turmeric; process until smooth. Return coconut milk mixture and remaining pureed lentil mixture to pan. Cover and simmer over medium heat 10 minutes. Remove from heat; stir in 1 teaspoon juice, salt, and pepper. Ladle about 1 cup soup into each of 4 bowls; top each serving with 1/4 cup salsa.