Then heat the oil in the pan and fry the onion until translucent. Add tomatoes and season well. Let simmer in the pan for about 3 - 4 minutes, then add the tortellini (the tortellini do not have to be pre-cooked!) And put the lid on the pan. Now the tortellini should be cooked over medium heat (turn every now and then). Finally, remove the pan from the heat, stir in the crème fraîche and serve hot.