One the foods that Sebastian will almost always eat is pasta - sometimes just with grated cheese. (He particularly likes Parmesan!)
So here's a simple recipe for a tomato sauce which works well with spagetti or other forms of pasta. It's certainly a good substitute for those tins of spagetti in sauce. Appropriate parental supervision during the preparation is, of course, required.
First, the sharp knives part! Peel and slice a medium-sized onion. (With smaller children, I like to peel and halve the onion myself, so that it lies flat and stable on the chopping board.) You could chop a clove of garlic too, if your child likes garlic. (Sebastian loves garlic bread!)
Squeeze the juice from half a lemon. The kids seem to like the brute-force squeezing!
Now, the hot bit. I like to use a large and heavy saucepan on the stove, since it is hard to accidentally knock off or spill. Put in a couple of tablespoons of olive oil and cook the onion (and garlic if used) for about five minutes, stiring all the time. This is an opportunity to show the kids the way that onions go soft and nearly transparent when they are cooked.
When the onions are soft, add a tin of chopped tomatoes. (It's a bit messy for kids to chop tinned tomatoes themselves!). Also add the lemon juice and a pinch of salt. This needs to be cooked very slowly, and stirred occasionally, until most of the liquid has evaporated.
Meanwhile, fill another large saucepan half-full with cold water, and add lots of salt and a tablespoon of cheap olive oil (to prevent the spagetti from sticking). Bring to the boil and then, and only then, add the spagetti - how much depends on the appetite of the kids! - and cook for about 10 minutes.
Once cooked, add a pint or two of cold water to the saucepan (also helps to prevent sticking - and drain immediately. Separate and serve in shallow bowls, spooning the tomato sauce over the top. You can add grated cheese or parmesan if you want, as well as freshly-ground black pepper.
The sauce can be made ahead of time and kept in the fridge for a few days.