Dissolve the vegetable bouillon cubes in a small amount of boiling water to create a concentrated stock.

Slice the onion.

Heat a little olive oil in a pot or large saucepan over medium heat.

Add the sliced onion to the pot and sauté for 2 minutes, until softened.

Chop the carrots into small pieces.

Add the chopped carrots to the pot with the onions and sauté for another 2-3 minutes.

Add the chopped tomatoes, lentils, and a generous squirt of tomato puree to the pot.

Pour in the prepared vegetable stock and the remaining water.

Bring the soup to a boil.

Reduce the heat to low and simmer for 25 minutes, or until the lentils are tender.

Serve hot.