Pick over and rinse the lentils and put them in a 4-quart saucepan. Cover them with 2 quarts cold water and add 2 tsp. salt. Bring to a boil over high heat. Lower the heat, partially cover the pot, and simmer until the lentils are slightly firm but tender and still intact, 20 to 30 minutes. Drain and run cold water over them. Drain again and transfer to a large bowl.
Sprinkle the lentils with the vinegar, 1 tsp. salt, and a few grinds of black pepper. Stir gently to combine, taking care not to mash the lentils. Stir in the oil, 1 Tbs. at a time, and finally, the scallions and garlic.
Let stand at room temperature for about 1 hour; then season to taste and serve.
Make Ahead Tips
For the best flavor, make this salad at least 1 hour and up to 3 hours before serving.
nutrition information (per serving):
Calories (kcal): 290; Fat (g): 11; Fat Calories (kcal): 100; Saturated Fat (g): 1.5; Protein (g): 13; Monounsaturated Fat (g): 7; Carbohydrates (g): 36; Polyunsaturated Fat (g): 1; Sodium (mg): 290; Cholesterol (mg): 0; Fiber (g): 9.