Student or Learner
Mel is just teasing Jim for having pizza without topping saying "gourmet cook", I can understand gourmet, but what is gourmet cook? He is actually not a cook. It seems an idiom.
Mel- Plain pizza? Uhh! You don't like anything on it at all?
Jim- I'm a purist.
Mel- You, mr. Gourmet cook, and you have naked pizza.That is just indecent.
A "gourmet cook" refers to someone who likes to cook very elegant cuisine - for example, someone who prefers to make homemade pasta noodles from scratch versus opening up a can of Spaghetti-Os. If Jim Clancy is not known for his prowess in the kitchen, then Melinda is more than likely being sarcastic - calling him a "gourmet cook" when he is having something so plain as a pizza without any toppings.