Combine King Red lentils, bulgur wheat or rice, onion and water in a large pot and bring to a boil over medium heat. Boil until soft and creamy, approximately one hour. Add stock and simmer for 10 minutes. With a hand-blender, blend soup for 3-5 minutes on low until thoroughly mixed and smooth.
In a small saucepan, heat butter until it becomes liquid. Stir in cayenne or pepper flakes.
When ready to serve, stir and remove soup from heat. Let rest for 10 minutes, then ladle into bowls. Drizzle butter and cayenne/pepper mixture into bowl and add a small amount of lemon juice and cumin.