Finely dice the bacon. Wash the onions and cut into rings.
Peel and roughly dice the carrots. Peel the potatoes and cut into small cubes. Fry the bacon in a saucepan.
Add the oil, add the potatoes, carrots and onions and fry while turning. Deglaze with 600 ml of water, add the lentils, bring to the boil and simmer covered for approx. 15 minutes.
Then season with salt, pepper and vinegar.
Heat butter in a pan, add fish and fry. Season with salt and pepper. Remove from the pan and deglaze the roasting fat with the lemon juice, bring to the boil. Arrange the lentil vegetables and fish, drizzle with the gravy.