Apple Crumb Cake

I found this recipe in a newspaper and again "tweaked it".

3 large apples, washed, cored and diced--leave skins on--they're great
2 tablespoon ground cinnamon
1 cup sugar (or Splenda)
1/2 stick of butter
1 cup flour
1 cup brown sugar
1 tsp vanilla extract
Walnuts pieces and raisins optional

Preheat oven to 325. Spray pryex dish with Pam. Lay apples on bottom and sprinkle with cinnamon and white sugar. Add walnuts or raisins on top. Set aside. Partially melt butter in microwave (where is softened but not melted completely). Add flour, brown sugar and vanilla extract to butter. Mix until sort of crumbly. Sprinkle on top of apple mixture and bake for about 45 minutes until top is brown.