Shape the meat into 2 equal-size patties, each one about 6 ounces and, ideally, slightly broader than the buns. Salt and pepper both sides of the patties.
In a medium cast iron skillet, cook the bacon over medium heat until slightly crisp. Remove the bacon. Pour off all but 1 to 2 tablespoons bacon fat from the pan and crank the heat to medium-high.
Cook the patties until they take on a nice char, 1 to 2 minutes, depending on the thickness.
Flip the patties and place first the bacon and then the cheese on the top of each burger. Cover the skillet and cook until the desired doneness, about 1 minute for medium-rare. If you prefer a less rare burger, simply cook another minute or two on each side.
Meanwhile, butter the buns and place them, cut side down, in another skillet over medium-high heat until nicely toasted, 2 to 3 minutes.
Slather 1 tablespoon Romesco on the bottom half of each bun. Place the burger patties on top and garnish with greens and 6 to 8 slices of pickled zucchini, if using. Place the top half of the bun on each stack of bacon cheeseburger spectacularness and demolish.