Step 1

Cook the bacon in a medium-sized pan over medium heat until crispy, about 10 minutes. Remove the bacon from the pan and pour out all but 2 tablespoons of the bacon oil.

Step 2

Add the onion to the pan and cook until they are golden brown, about 10 minutes.

Step 3

While the onions are cooking, mix the mayonnaise and chipotle peppers in a small bowl.

Step 4

Remove the onions from the pan and put the bread into the pan. Let it toast for 1-2 minutes, until lightly golden.

Step 5

Spread the chipotle mayo on the toasted bread then top with the caramelized onions, crispy bacon, tomato slices, and arugula. Put the other slice of bread on top then serve right away.