Start by heating up a large fry pan big enough to hold all the scallops.
Add the bacon and cook for about 3 minutes until crisp and the fat is rendered from the bacon.
Remove the bacon from the pan with a slotted spoon or slotted spatula and transfer to a plate lined with a paper towel to absorb any fat. The recipe says to pour off all but 1 tablespoon of fat but I didn't find that necessary. Maybe my bacon isn't so fatty.
Add the scallops to the pan, season with salt and pepper and pan fry over medium-high heat for 3 minutes. When you flip the scallops over, they should be nice and brown.
Add the onion to the pan and cook for another 3 minutes and transfer to a plate.Don't make the mistake I did by lining the plate with a paper towel to absorb any juices that may release out of them when resting. These juices are going to be added back to the pan when making the sauce. Silly me! Deglaze the pan with the white wine, then add the reserved grapefruit juice (approximately 3 tablespoons) to the pan and bring to a simmer. Be sure to scrape up any browned bits stuck to the pan with a wooden spoon or spatula. Let this cook for about a minute or two.
Strain this liquid into a heatproof cup (I used my pyrex measuring cup) and return the strained liquid to the pan.
Add the capers and butter and cook until the sauce thickens to a nice consistency. Be sure to stir the sauce while it is cooking and give the pan a shake now and again to keep it moving. This should take about 3 minutes.
Add the scallops back to the pan along with the juice that you didn't let get absorbed onto a paper towel.
Add the grapefruit slices and reserved bacon pieces into the pan, then flip each scallop so it gets coated with the sauce.