Heat oil in a large saucepan over medium heat. Add the onion, garlic, carrot and celery, cook, stirring often, for 5 minutes or until onion softens.
Add the tomato and stock and bring to the boil. Add the lentils and stir until well combined. Reduce heat to low and cook, stirring occasionally, for 20 minutes or until the lentils are tender and the soup thickens. Taste and season with salt and pepper. Sprinkle over fresh coriander.
Meanwhile, heat a chargrill pan over medium-high heat. Brush both sides of the bread slices with oil and crushed garlic. Chargrill for 2-3 minutes each side or until toasted. Spread with the feta then place on a serving tray and season with pepper.
Combine the parsley or coriander and lemon rind in a small bowl. Ladle the soup among serving bowls and sprinkle with the parsley mixture.