Here are the following ingredients:
Here are the following shopping items to buy:
Follow these cooking methods/directions:
Melt butter and olive oil over medium heat in medium saucepan; heat until butter is melted. Cook onion, stirring occasionally, for about 15 minutes or until very soft and caramelized (reduce heat as necessary to prevent burning). Stir in balsamic vinegar and season with salt and pepper to taste. Set aside.
Meanwhile, grill the sausages on a lightly oiled grill in a closed preheated barbecue over medium-high heat (400°F/200°C) for 10 to 14 minutes, turning often, or until a digital instant-read thermometer inserted lengthwise into centre of each sausage reads 160°F (71°C). Transfer to a plate and keep warm. Toast the buns lightly, split side down on the grill.
Assemble sausages into toasted buns and top with the Caramelized Onions and chunks of tomato to serve.