Heat oil in a large skillet over high heat. Add onions and salt; cook, stirring frequently, until the onions begin to brown, about 5 minutes. Reduce heat to low, add 2 tablespoons water and cook, stirring frequently, until the onions are golden brown and very soft, 13 to 15 minutes.

Stir in lentils, bulgur and 1 1/4 cups water. Bring to a boil over high heat. Reduce heat and simmer, stirring occasionally, until the water is absorbed, 7 to 8 minutes.