Heat a large Dutch oven over medium-high heat. Add oil to pan; swirl to coat. Add onion and garlic to pan; sauté 4 minutes. Stir in 3 cups broth, lentils, and next 4 ingredients (through red pepper); bring to a boil. Cover, reduce heat, and simmer 10 minutes or until lentils are tender. Place the lentil mixture in a blender. Remove center piece of blender lid (to allow steam to escape); secure blender lid on blender. Place a clean towel over opening in blender lid (to avoid splatters). Blend until smooth. Return lentil mixture to pan over medium heat. Add remaining 1/2 cup broth, 1 cup water, and pumpkin to pan; cook 3 minutes or until thoroughly heated. Stir in ginger and lemon juice. Ladle 1 1/2 cups soup into each of 4 bowls; top each serving with about 2 teaspoons yogurt, 1 tablespoon pumpkinseeds, and 1 tablespoon cilantro.