It looks like a regular pie. It has magenta filling that is made with seaberries.
Role in episode
A fish brings his Grammy's favorite seaberry pie to the Krusty Krab. Squidward suddenly comes flying at the pie and smashes into it, and since he is allergic to seaberries, he puffs up. Patrick thinks that he is a monster that is going to attack SpongeBob, so Patrick attacks Squidward. Squidward decides to change the name on his restraining order from SpongeBob to Patrick so that Patrick will leave him alone.