Cut up some chorizo or chipolatas (or both) into chunks, and fry in a couple of tablespoons of oil.
In a large pan, soften a chopped onion, at the end add a finely chopped clove of garlic. Keep frying gently for another minute.
Add the sausage (including the oil you fried it in).
Add 250-500g of lentils, and enough water to cover them. And a bit more water. Maybe a stock cube while you’re at it, and a bay leaf. You could probably try adding some stout or similar here, too. Or a teaspoon of paprika. Maybe some carrot.
Bring to boil, turn down the heat and simmer for 30-45 min or so until cooked, sometime before the end taste and add salt if needed.