To prepare a three cheese quiche with tomato and onion salad recipe, you will first need to prepare the ingredients. Preheat the oven to 375?F (190?C) and prepare your oven rack to line the bottom of the pie dish with parchment paper. In the bowl of an electric mixer, cream together the butter, sugar, and eggs until light and fluffy. Gradually add the milk and mix until the mixture reaches stiff peaks. Add the ricotta cheese and beat until melted. Pour the egg mixture into the pastry shell and bake for 20 to 25 minutes or until golden brown. Remove from oven and allow to cool before serving.