The sauce can probably serve four people if you make enough pasta and serve with a side salad or some bread.
Cut the squash and onions into small pieces, then fry in a shallow pan in olive oil for ~10 minutes until the onion is cooked through. Add the garlic and stock cube and fry for 30 seconds or so until fragrant. Deglaze the pan with the white wine, or water.
Add the tinned tomatoes and leave to simmer for about half an hour, stirring often until the squash is cooked through. Top off with water from the cooking pasta if the sauce begins to stick to the pan. Add the lentils and leave to simmer until they are heated through. Add the rosemary and sage, along with salt and pepper to taste.
Meanwhile, boil a saucepan of water and add salt and a splash of olive oil. Add the pasta and cook for ~15 minutes. Retain about a cup of water before draining the pasta.
Once the sauce is thick and the squash is nicely soft, take it off the heat. In the saucepan, heat some olive oil. Add in the pasta and sauce. Mix through, adding the retained water slowly until the pasta is evenly coated and the sauce is a good consistency. Take off the heat and serve.