To make pan-seared scallops with bacon and spinach, brown four slices of center-cut bacon in a heavy skillet on high heat until the bacon is brown and crispy. Remove the bacon and drain the bacon fat, reserving one tablespoon in the pan. Crumble the bacon and set it aside.
Pat 1 1/2 pounds of jumbo sea scallops dry with paper towels and season the scallops with 1/4 teaspoon of kosher salt and 1/8 teaspoon of freshly-ground black pepper. Add the scallops to the hot pan and cook them in the bacon fat for about 2 1/2 minutes on each side, until done. Transfer the scallops to a plate or dish and keep them warm.
Reduce the heat to medium-high and sauté 1 cup of chopped onion and 6 sliced garlic cloves for three minutes, stirring frequently. Add 6 ounces of fresh baby spinach to the pan and cook the mixture for one minute. Stirring frequently, add another 6 ounces of fresh baby spinach and cook for two minutes until the spinach is slightly wilted. Remove the spinach from the heat and season the mixture with 1/8 teaspoon of salt and 1/8 teaspoon of pepper.
Evenly divide the spinach mixture on four plates and top each serving with the crumbled bacon and scallops. Serve the scallops with wedges of fresh lemon, if desired.