Boil the lentils in plenty of water, with a vegetable stock cube crumbled in for extra flavour. When the lentils are soft but still holding their shape (around 10 minutes), drain them, and transfer to a food processor.
Add the eggs, onion powder and plenty black pepper - you may not need extra salt unless you used low sodium stock. Blitz thoroughly until smooth.
Lightly spray a non-stick frying pan with oil, and place over a medium heat. Add around 1/6 of the lentil mixture to the pan, and use the back of a spoon to spread it out into the shape of a pancake. If the tortilla is too thin or too thick it will break a bit more easily - it might take a little practice to find the perfect size.
Thoroughly cook the tortilla until the underside is starting to turn golden. Very carefully use a large spatula to turn the tortilla over, and repeat with the other side.
Transfer the cooked lentil tortilla to a plate, and repeat with the remaining mixture. You should end up with around 6 tortillas in total. Serve warm or at room temperature.