The ornamental design for a commercial microwaveoven, as shown and described.
FIG. 1 is a front elevation view of a commercial microwave oven, showing my new design;
FIG. 2 is a left side elevation view thereof;
FIG. 3 is a right side elevation view thereof;
FIG. 4 is a top plan view thereof; and,
FIG. 5 is a front, right side perspective view thereof.
Rear and bottom views are omitted as they form no part of the claimed design. The broken lines immediately adjacent the shaded areas represent the bounds of the claimed design while all other broken lines are directed to unclaimed features of the commercial microwave oven and are for illustrative purposes only; the broken lines form no part of the claimed design.