Take a spacious bowl and combine the flour, sugar, yeast, and salt by stirring them well.
In another bowl, blend the softened butter, egg, and milk with an electric mixer on low speed until it forms a well-combined mixture. Transfer the liquid mixture to the bowl of dry ingredients and mix it on low speed until the dough detaches itself from the sides of the bowl.
Cover the dough and allow it to rise in a warm place for about 45 minutes.
Then, generously spray a 9" springform pan with nonstick baking spray.
After the dough has risen, press it uniformly into the base of the prepared pan.
For the Middle Layer
In a mixing bowl of medium size, combine the instant pudding and milk until thoroughly blended. Allow the mixture to sit for approximately 5 minutes to thicken.
Next, in a larger bowl, combine the ricotta, sour cream, sugar, lemon juice, and one-third of the prepared pudding. Mix the ingredients together until they are fully incorporated. Take note that the remaining two-thirds of the pudding mixture will be used for the top layer.
Once the mixture is evenly blended, spread it smoothly and evenly over the crust layer.