The ornamental design for a minidonutgrillplate, as shown and described.
FIG. 1 is a top front right perspective view of a mini donut grill plate showing my design therefor;
FIG. 2 is a top plan view thereof;
FIG. 3 is a rear elevational view thereof, the front elevational view being identical, the bottom portions shown in phantom line and forming no part of the design;
FIG. 4 is a right side elevational view thereof, the left side elevational view being identical, the bottom portions shown in phantom line and forming no part of the design; and,
FIG. 5 is a bottom plan view thereof, the central parts shown in phantom line and forming no part of the design.