The ornamental design for a restaurantbuilding, as shown and described.
FIG. 1 is a top plan view of a restaurant building showing my new design,
which includes three radially extending arms spaced at equal angles from
one another around the periphery of the building;
FIG. 2 is an elevational view thereof, looking directly at the end of one
of the arms; and
FIG. 3 is an elevational view thereof taken at an angle of sixty degrees to
the elevational view of FIG. 2.