FIG. 1 is a perspective view of a tomato corer showing my new design. FIG. 2 is a front elevational view thereof. The rear elevational view is identical to FIG. 2. FIG. 3 is a side elevational view thereof. The opposing side elevational view is identical to FIG. 3. FIG. 4 is a top plan view thereof; and, FIG. 5 is a bottom plan view thereof. The broken lines in the figures are for illustrative purposes only and form no part of the claimed design.