Meat sauce: chop the vegetables then transfer them to a saucepan with the oil and fry on the semi-rapid burner. Add the minced meat and fry for a few minutes.
Pour in the tomato purée, with salt and pepper to taste. Cook over a low heat for about 30 minutes, adding a very little hot water if necessary.
Béchamel sauce: melt the butter in a saucepan over an auxiliary burner and add the flour. Stir for 1-2 minutes. Then pour in warm milk a little at a time, stirring to prevent lumps from forming. Thicken the béchamel sauce over a low heat, stirring continually. When it is dense and velvet-smooth, add salt and pepper to taste and flavour with the nutmeg. Set the béchamel sauce to one side.
Put a pan of salted water on the triple ring burner, bring to the boil and boil the tagliatelle. Drain the tagliatelle when still slightly firm ("al dente") and mix it with the meat and béchamel sauces, then transfer it to an oven dish on a baking tray and place on the middle shelf of a Glem static oven at 190° for 15/18 minutes. Finish cooking using the grill function for 2-3 minutes.