Check the lentils carefully for debris, and rinse thoroughly. Because of the size and color of these lentils, pebbles and other natural debris may remain despite our best efforts to sort them before packaging.
In a pot over medium-low heat, warm the olive oil. Add the garlic, onion, bell pepper, and carrot and cook until softened, 10 to 15 minutes.
Stir in the pimentón and tomato sauce and simmer until combined. Stir in the lentils, potatoes, and broth. Bring to a boil, then reduce to a simmer and cook until the lentils and potatoes are tender, 35 to 40 minutes, adding more liquid if needed.
Season to taste with vinegar, salt, and pepper. Garnish with parsley.
