In a shallow dish, whisk together flour, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Place pork slices on a clean work surface, and press with the heel of your hand until each is about 1/3 inch thick. Lightly dredge pork in flour mixture, turning to coat completely; tap off excess.
In a 12-inch nonstick skillet, heat 1 tablespoon oil over medium-high heat. Working in batches so as not to crowd pan, add pork; sear until browned, about 2 minutes per side. Transfer to a platter. Add more oil to skillet, if needed. Cover with foil.
Add garlic; cook, stirring, until fragrant, about 1 minute. Add capers, if desired, and citrus juices. Bring to a boil, stirring up any browned bits from bottom of pan. Cook until sauce is slightly thickened, 2 to 3 minutes. Season with salt and pepper, as desired. Serve sauce over pork.