Each topping listed on the menu appears on the pizza at least once. After counting the number of appearances of each topping, we can index into the name of that topping by the number of times it appears. For example, since there are nine anchovies, we take the ninth letter of ANCHOVIES, giving an S.
The full counts are as follows:
Green Olives – 1
Black Olives – 2
Mushrooms – 2
Tomatoes – 5
Green Peppers – 3
Banana Peppers – 3
Feta Cheese – 1
Artichoke Hearts – 2
Pineapple – 4
Eggplant – 1
Canadian Bacon – 1
Pepperoni – 6
Sausage – 3
Anchovies – 9
Meatballs – 4
Taking the clued letters in order reading down the columns gives the answer, GLUTEN-FREE CRUST.