Soak the red lentils. Soak the lentils in water for 30 minutes.
Sauté the onions and garlic. Heat olive oil in a pot, add the onions and cook for about 3 minutes, stirring often, until fragrant and translucent. Then add the garlic and cook for 30 seconds.
Add the tomato paste and herbs. Cook for a few minutes until caramelized.
Pour in the broth, soaked lentils, and canned tomatoes. Stir, then bring the mixture to a boil. Once it starts to boil, reduce the heat to a simmer. Season with a pinch of salt and black pepper.
Simmer the sauce. Allow the sauce to simmer gently for about 20 minutes, or until the lentils are al dente and the sauce has reduced into a thick, rich consistency. Give it a taste and adjust the seasonings as needed.
Cook the pasta. While the sauce simmers, bring a large pot of generously salted water to a rolling boil. Drop in your pasta and cook until it is just al dente. Right before draining, scoop out a ladleful of the starchy pasta cooking water and set it aside
Finish the sauce. Just before taking it off the heat, stir in a splash of balsamic vinegar.
Serve. Spoon the hot bolognese over freshly cooked pasta and garnish with chopped fresh parsley.