In a medium pan, sweat the onions in the oil for about 5 min until soft and starting to turn golden.
Add the lentils, feta, spinach, pine nuts and the pesto. Stir then add 4-5 tbsp water to loosen.
Season with generous amounts of black pepper, and salt to taste.
Notes
Switch ingredients and add to it according to what you have available, e.g. swap feta for fried halloumi, add some spices. If you don't have pesto, add a tbsp lemon juice.