Apparently it's more common than I thought to gag on raw tomatoes even while having no problem with tomato sauce:
People like me just lack certain key taste receptors, preventing us from appreciating the rich, sweet, meaty flavor of raw tomatoes that the rest of you are always rhapsodizing about. The problem is that tomatoes have something on the order of 400 volatile compounds and who knows which one of those (or combination thereof) might be responsible for the harsh reaction many of us experience in response to raw tomatoes?
Frankly, the scientific community has been sadly remiss in getting to the bottom of the mystery of why raw tomatoes make some of us gag, despite a few scattered flavor studies. But they’re hot on the case of cilantro, an even more polarizing herb. I love cilantro. To me, it tastes fresh and citrusy with just a tinge of an herbal edge to it. But to some people, it just tastes like soap. Or worse. They have as strong a visceral reaction to cilantro as I have to fresh raw tomatoes.
Of course, it could be the gloppy, lumpen nature of tomatoes that makes us gag, too. I'll stick with purée.