Cocoa powder is considered a spice, and is legal on Atkins.
Pumpkin pie? Well, get a large can of pumpkin (not pie mix). Add 1/4 cup of heavy cream, 1.5 teaspoons of pumpkin pie spice (some people may like more - taste it to see), 4 eggs, and splenda to taste (I use 3/4 cup, but some people like it sweeter. Taste it to see.) Bake at 350 degrees for about an hour.
I chill it, spoon it into individual tupperware containers, and bring it for my mid-morning snack at school.
There are great recipes in the recipe forum on this site. There are also places like Linda's Low Carb recipes (do a google search!) that have some amazing stuff!
Yes, you are supposed to be eating non-processed foods. What is processed about a can of pumpkin? It's just been cooked and canned - that's ok.