In a large frying pan over medium heat, fry the bacon until crisp, turning once. Remove and drain on paper. Heat baked beans in a saucepan over medium heat. Pour a tablespoon of the rendered bacon fat into a small frying pan and bring both frypans to medium high-heat.
In the small frypan add the sliced onion then cook until translucent. Meanwhile crack the eggs into the larger pan and cover. Cook until whites are firm and yolks are slightly runny, about 5 -7 minutes. Transfer to plate.
Serve bacon, eggs, beans and onion on a plate with hot buttered toast.