I just use veggie stock.
Onion, garlic and olive oil in the pot then add the veggie stock, chop up all your veggies and throw them in, add your lentils and pasta, let it cook and then serve and season with salt n pepper. Enjoy with some nice toasty bread. Quick and easy. You could even make it a minestrone by adding a cpl cans of tinned tomatoes and some herbs.