Cook the tomatoes down hard with the onion until the pan is nearly dry and the sauce is sweet rather than sharp — that reduction is the entire recipe. Make four hollows, break an egg into each, and give it eight minutes in the oven.
The method above is what decides the dish, not a step-by-step recipe. The link runs a web search on the name: this page has no vetted sources of its own, and will not invent any.