The ornamental design for a countertopcookingappliance, as shown and described.
FIG. 1 is a perspective view of the countertop cooking appliance according to my new design in a first configuration;
FIG. 2 is a front view of the appliance of FIG. 1;
FIG. 3 is a left side view of the appliance of FIG. 1;
FIG. 4 is a top view of the appliance of FIG. 1;
FIG. 5 is a right side view of the appliance of FIG. 1;
FIG. 6 is a rear view of the appliance of FIG. 1; and,
FIG. 7 is a bottom view of the appliance of FIG. 1.
The rear and bottom views are provided for reference only and form no part of the claimed design. Components shown in broken lines are for environment only and form no part of the claimed design.