For the Salad:
Bring a large pot of salted water to a boil over high heat. Add the lentils and cook until tender, stirring occasionally, about 18 to 20 minutes. Drain and let cool for 5 minutes. Place lentils and remaining salad ingredients in a large salad bowl.
For the Vinaigrette:
Place the lemon juice in a small bowl. Slowly add the oil, whisking constantly, until combined. Season with salt and pepper, to taste
Pour the vinaigrette over the salad and toss well.