After some trial and error, I've found that the best method to remove the tomato tops is to use a serrated knife. Slice about 1/3 to 1/2 of an inch below the top to remove the whole stem. Then, use a spoon to scoop out the insides of the tomatoes. This can be a great time to use a grapefruit spoon if you have one. That's it! I also recommend salting the inside of each tomato and setting it upside down to drain off the excess liquid.