Turmeric gives this creamy soup a deep golden color, and the red lentils lend it a slightly sweeter flavor than brown or green lentils would. The lentils also provide niacin and plenty of folate, a B vitamin that may help delay cognitive decline.
Heat oil and butter in a Dutch oven over medium-high heat. Add onion, ginger, and jalapeño; sauté 4 minutes or until tender. Stir in 6 cups water and next 4 ingredients (through five-spice powder); bring to a boil. Cover, reduce heat, and simmer for 15 minutes or until lentils are tender, stirring occasionally.
Place one-third of 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. Pour pureed lentil mixture into a large bowl. Repeat procedure twice with remaining lentil mixture. Stir in cilantro and juice. Serve immediately.