1) To make the first layer, heat your 9" or 10" electric skillet to 275°F. Add the butter, and let it melt while the skillet heats. Note: This recipe requires that your skillet have a lid. If it doesn't you'll have to fashion a cover out of aluminum foil.
2) When the butter is melted, sprinkle the sugar evenly on top. Press it down with the back of a spoon to make an even layer.
3) Turn the skillet to low. Top with the fruit or berries. Sprinkle with the Pie Filling Enhancer, if you're using it; it'll make the syrup that bubbles up around the cake thicker.
4) To make the second layer, beat the butter and sugar in a medium-sized mixing bowl till smooth.
5) Beat in the egg, then the vanilla, salt, and baking powder. The mixture will look slightly curdled; that's OK. Turn your skillet back to 275°F, so it's up to temperature when you're ready to add the cake batter.
6) Gently beat in the flour alternately with the milk, beginning and ending with the flour.
7) Dollop the cake batter atop the berries, spreading it out as best you can. Don't be too particular about making it perfectly smooth; the dessert will bake up unevenly anyway, so don't fuss.
8) Put the lid on the skillet, and bake the dessert for 25 to 35 minutes, till the cake is set and the fruit is bubbly. Check it frequently, to make sure the bottom isn't burning; remove the lid, and use a spoon to poke through the cake to the skillet. If it seems to be browning on the bottom too quickly, reduce the heat.
9) When the cake tests done — a toothpick or cake tester inserted into one of the thicker pieces of cake comes out clean — turn off the skillet.
10) Remove the cover from the skillet, and use a large spoon or spatula to scoop servings into bowls. Serve warm, with ice cream or whipped cream, if desired.
11) Yield: about 12 servings.