There are lots of weird cookies sold all over the world. I don't imagine that Japan has the market cornered on such things, but I do see more of them sold in Tokyo than I ever saw back home. In the U.S., usually weird things were so regional that you couldn't get them unless you went to some place which claimed to be "the capital of (food type)". For instance, I bet you can get cheese-flavored ice cream in Wisconsin or cajun cookies in New Orleans, but neither would be sold in shops in big cities.
These red onion langue du chat (cat's tongue) cookies are from Hokkaido. It seems that everything odd that I find here is from Hokkaido. Though I thought at first that they might be just shaped like onions, my research seems to indicate they are savory cookies with spices that compliment onion flavor and have a cheese cream sandwiching them together. They are shown served with wine. I wasn't really tempted, not because they aren't interesting, but because I didn't feel like paying 600 yen ($9.14) for a box of 6 of something that I am not at all sure is going to be tasty.