Heat 1 tablespoon of olive oil in a large saucepan over medium heat.

Add the finely chopped brown onion and crushed garlic to the saucepan.

Cook, stirring often, for about 5 minutes, or until the onion softens.

Pour in the diced tomatoes (3 cans) and vegetable stock (1 liter).

Bring the mixture to a boil.

Add the split red lentils (175 g) to the saucepan and stir until well combined.

Reduce the heat to low and let the soup simmer.

Cook, stirring occasionally, for approximately 20 minutes.

Continue cooking until the lentils are tender and the soup thickens to your liking.

Taste the soup and season with salt and pepper to your preference.

Serve hot.