Our favourite pasta sauce is from the River Cottage Baby and Toddler Cookbook (which is great, btw).
Basically, it's butternut squash, a fennel bulb, a couple small onions, a carrot, and several cloves of garlic (wrap these in foil to roast), then roasted in the oven with olive oil until they all start to caramelise, then blend with a hand mixer or food processor with about 200ml of vegetable or chicken stock (more or less depending on the consistency). Serve over pasta with grated cheese on top.
It's delicious!