Start by boiling your lentils in salted water. They want about 20 minutes.
In a pan pour 1 tbsp. olive oil and once heated add the beans, onion and pepper. Add salt and pepper. Cook for 8-10 minutes. Put it aside.
Pour all the ingredients for the dressing into a jar. Close with the lid and beat well.
Toss the lentils, vegetables and dressing in a large bowl. Mix well. Add the grated feta and mix again.
Enjoy.