Rinse the red lentil with water to remove any debris
Using a food processor or a knife, mince the red onions
Juice the lemon to obtain fresh lemon juice
In a large cooking pot, at medium-low heat, add the olive oil and let it become hot for about 2 minutes. Then add the minced red onions and sauté for 5 minutes, occasionally stirring until the color of the onion becomes translucent.
Next, add the red lentils, spices, and water to the cooking pot and bring to boil. Then lower the heat of the stove to low and close the lid. Allow the red lentil soup to simmer for 45 minutes.
Afterward, remove the soup from heat and add the lemon juice.
Optional: Using a hand-held blender or a stand-alone blender, blend the lentil soup until it is creamy and without any lumps.