Prepare the guacamole: In a medium mixing bowl, combine the avocado, tomato, cilantro, lime juice, salt and jalapeno. Stir to combine and then set aside while preparing the burgers.
Prepare the burgers: Season each patty with steak seasoning on both sides before cooking. You can use a skillet, grill pan, or a grill over high heat to cook your burgers to desired degree of doneness. When the burgers are almost finished cooking, toast the buns in a toaster oven, a dry skillet, or on the grill.
Assemble the burgers by layering the bottom half of each bun with leaves of lettuce, a burger patty, a slice of cheese, slices of onion, and slices of tomato. Top with a generous scoop of guacamole, and cover with bun.