In a large pot, heat the olive oil or butter over medium heat. Add the chopped onion and sauté for about 5 minutes until softened and translucent, which will create a flavourful base for the soup.

Add the chopped carrot and potato to the pot, stirring for an additional 3 minutes. This step helps soften the vegetables slightly and blend their flavors with the onion.

Stir in the tomato paste, cumin, and paprika. Cook for another 2 minutes, allowing the spices to release their aromas and the tomato paste to develop a deeper flavour.

Add the rinsed red lentils to the pot, stirring well to coat them in the spices and tomato paste. This step ensures the lentils absorb maximum flavour from the base ingredients.

Pour in the broth (or water) and add salt and black pepper to taste. Stir to combine all ingredients. Increase the heat and bring the mixture to a boil.

Once boiling, reduce the heat to low, cover the pot, and let it simmer for about 25-30 minutes, or until the lentils and vegetables are fully tender. Stir occasionally to prevent any sticking at the bottom.

Using an immersion blender, blend the soup until it reaches a smooth, creamy consistency. If you prefer a chunkier texture, blend only partially. Adjust seasoning with additional salt or pepper if needed.

Serve the Mercimek Çorbası hot, garnished with fresh parsley if desired. Accompany each bowl with a lemon wedge for squeezing, adding a refreshing brightness to the dish. Serve with warm bread for a truly satisfying Turkish meal.