Bring a medium saucepan of heavily salted water to a boil over medium-high heat.
Rinse dried lentils in a strainer, then add to boiling water.
Cook for 15-20 until lentils are tender but not falling apart.
While the lentils cook, make the dressing.
Add all dressing ingredients to a blender and blend for 20-30 seconds. The dressing should be smooth and thickened, with a little bit of texture from the walnuts.
When lentils are done, strain and add to a large serving bowl with cabbage, tomatoes, and green onions. Break up the feta and add to the bowl.
Drizzle the salad with the toasted walnut dressing and toss well.
Serve, or refrigerate as this will keep well for 4-5 days.