Melt the butter over medium heat in a medium sized saucepan. Stir in the flour and cook for 2- 3 minutes.
In the meantime, warm the broth in the microwave this isn't necessary but it will make it less likely that you will have lumps. Add the warm broth and the lemon juice to the flour mixture. Cook and stir for a couple minutes, til its thickened.
Add Bacon and cheeses, stir until they have melted. Serve with crackers or tortilla chips.