In a bowl, add the beef, mustard, salt and pepper. Mix with your hands to combine.
Grab your bundt tin and press the meat mixture into it to form a large circle. Turn out on a wire rack set over a lipped baking sheet and gently press the circle flat until it’s 2 inches thick.
Place each piece of bacon around the meat ring, overlapping them and tucking underneath.
Bake for 20 minutes in the hot oven and then turn the oven to grill and grill for 10 - 15 minutes until the bacon is crisp. Quite a lot of fat will collect in the bottom of the baking sheet, which is why it’s best to have the meat ring on a wire rack.
In a small bowl mix together the ingredients for the burger sauce and set aside.
Arrange the bottom of each roll in a circle and place the meat ring on top of buns. Add lettuce, onion and tomato on top of the meat ring then place the top part of the buns around the top of the meat ring.
Place burger sauce in the centre of the meat ring. Slice and serve immediately.