Simple way to slice a few grape tomatoes all at once.
Get two lids that are the same size. I just used two from some old chinese take-out. The lids can be bigger or smaller than the ones I used, it just depends on how many grape tomatoes you're trying to cram onto them and slice all at once.
Find a good, sharp knife (serrated knives work best) to slice through the tomatoes.
Squeeze as many tomatoes as you can onto one lid and then place the other lid on top of them.
Take that serrated knife you grabbed and, while placing one hand on top of the lids and tomatoes, slice on through those red ovals.
Tada! You just cut your cooking time in half now that you don't have to slice each tiny tomato separately!