Peel and finely chop the onion. Peel and dice the sweet potato.
Heat the olive oil in a pan over medium heat. Sauté the diced sweet potatoes and onion for about 15 minutes, stirring regularly. Add the spinach leaves.
In a bowl, break the eggs and season them.
Whip them into an omelette and pour them into a 20 cm diameter springform pan. Add your preparation as well as the cooking oil.
Bake for about 12 minutes until the omelet is set. Take out of the oven and let cool.