Put the butter with 125 gr. of water in a pot and bring to the boil. Remove from the heat and add the flour and salt. Bring to the boil again for 2-3 minutes, stirring quickly. As soon as the mixture does not stick to the sides of the pot, remove from the fire.
Let the dough cool for 10 minutes. Add the beaten eggs bit by bit and the garlic and stir. Let the dough rest while you prepare the tomato sauce.
Heat the olive oil in a pot and sauté the onion. Add the tomatoes and three tablespoons of water and cook for 10 minutes. Put the sauce in a food processor. Add the basil, salt and pepper and puree it.