In a large saucepan, melt the butter over medium heat. Sauté the veggie burgers, about 4 minutes per side, until browned and cooked through. (Morningstar burgers are meant to be cooked directly from the freezer, and the purpose of cooking is just to warm through. If you are cooking a fresh or homemade veggie burger, your cooking time will vary; be sure not to get the pan too hot or the burgers will blacken.)
Meanwhile, toast the burger buns.
Spread the toasted buns with garlic aioli or mayonnaise.
Notes
*You can usually buy tzatziki in the same place you would find hummus or refrigerated salad dressings. Look for a version that contains dill, garlic, and cucumber for the most delicious results!