In a sieve, briefly rinse lentils in running water. Add, along with chopped onion, to 2 cups water in a medium-sized pot. Set on medium-high heat, and bring to a boil. Keep pot uncovered and boil for 10 minutes, stirring frequently and watching that the lentils don’t boil over. Reduce heat to minimum, and add all seasoning. Stir well and cover. Simmer for 15-20 minutes. While lentils are thickening, sauté onion rings in olive oil until golden brown. Set aside. Remove lentils from heat, and stir in lemon juice. Top with browned onions and yogurt or sour cream.