Cook the aromatics: Heat the oil and cook the onions, celery, carrots and garlic for 10 minutes on medium heat. Stir intermittently to avoid burning so keep the heat low if necessary. While the soffrito cooks, add the tablespoon of butter, stir it in and continue cooking until the 10 minutes is done.
3 tbsps. olive oil, 1 onion, diced, 3 cloves garlic, finely chopped/minced, 2 carrots, chopped, 2 celery stalks, rinsed and chopped, 1 tbsp. butter, unsalted, pinch of salt
Lentils: Add all the ingredients from the lentils group and stir it all in, including the stock and the additional water from the empty tomato can. Increase the heat, bring to a decent simmer.
2 cups lentils, 410 grams canned diced tomatoes, 1/2 cup water into the empty tomato can and swirl, 1/2 cup red wine, or substitute with stock or water, 2 litres stock, or 8 to 10 cups of water, 2 to 3 bay leaves, 1 tsp. salt and pepper, 1 beef cube in a cup of boiling water
Simmer: While the lentils simmer the water on the surface will create foam like scum, use a large spoon to skim the surface and discard the foam. You may have to do this twice. Place the lid on the pot and leave it to simmer for 40 minutes but check at least twice to make sure the lentils have enough water and if they need more, add.
Remove the bay leaves and stir the lentil soup and taste for seasoning. If your lentils need more water, add a little at a time and stir it in. Serve with fresh lemon, and chopped parsley.