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Oh, I haven't gotten any yet - I just looked up to see where to get them. I can't believe they go to all the trouble of cutting patties with a Texas-shaped cookie-cutter, just for us'ns!
It occurred to me you might have meant for me to tell more about the onionburgers from Oklahoma - the instructions how to fix some similar at home.
Here's the whole pictorial. The key is to slice the onions very, very, very thin. I have a mandoline I used (a Chinese kitchen thingy - very cheap or very expensive, depending on where you find one - use it to hand slice veggies - very sharp) to make them paper thin.
http://www.ahamburgertoday.com/archives/2005/10/recipe_onion_bu_1.php
Also, get the best beef you can get your hands on. I don't normally fix burgers in a skillet - gotta grill or broil 'em - but these were pretty good.
(Another neat thing to use a mandoline for is very thin-sliced potatoes, to make see-thru baked potato chips. You just put two very, very, very thin slices of white or Idaho potato together with butter or olive oil and a small sprig of dill or thyme or cilantro or chives or scallion tops sandwiched in the middle.
Fill up a cookie sheet with them and brush again on the outside with butter or oil, then salt and pepper them. Bake at 400° until they're crisp, about 25-30 minutes. They are transparent and you can see the "treat" inside.)