Put the cubed bread in a baking tray, toss in a sprinkle of herbs and a bit of olive oil. Toast on a high grill setting in the oven until crispy, then turn them over. Sprinkle with cheese and toast a bit more until the cheese has melted and become crispy - just enough so it doesn't burn. Let it cool for a few minutes.
For the Soup
Add the onion and olive oil to a large saucepan over medium heat. Fry the onions until they soften, then add the garlic, ground cumin and coriander until it becomes fragrant.
Next, add the lentils and stir until they are coated, then add the stock and simmer on low for 40-45 mins until the lentils disintegrate.
Remove from the heat, stir in the lemon juice and season to taste. Dish up, sprinkle with croutons and coriander leaves.