Heat the oil in a pan. Sauté the onions for approx. 2 mins. Add the spinach, cover and keep warm, remove the pan from the heat. Combine the cream, eggs and cheese, mix in with the spinach, season.
Roll out the pastry and place on a tray (approx. 30 cm in diameter) along with the baking paper. Shape the pastry edges into a wavy design, prick the base firmly with a fork. Spread the spinach filling over the base. Arrange the tomatoes on top.
Approx. 35 mins. on the bottom shelf of an oven preheated to 220°C.