Take a thin slice off the bottom of each tomatoes so they are able to sit upright. Slice the top off and remove the core and seeds with a melon baller or strawberry huller.
To remove excess moisture from the tomatoes (so your filling won't get watery), sprinkle each inside with a bit of salt, then turn over onto a paper towel and allow to drain for 15 minutes. Take a small corner of a clean paper towel and quickly wipe away the remaining moisture from the inside of each.
Prepare filling of your choice then place in a pastry bag (or ziploc bag with the corner snipped off). Gently squeeze filling into each and garnish with toppings of your choice.