In the same skillet, heat the remaining tablespoon of olive oil over medium-high heat. Add the onions with a pinch of salt and pepper. Cook, stirring often, until lightly softened, about 2 minutes. Stir in the apples. Reduce the heat to medium; cover and cook, stirring occasionally, until the apples and onions are golden and tender, 4-6 minutes longer (if the drippings on the bottom of the pan start to look too dark, add a splash or two of water). Transfer the apples and onions to the plate with the pork (reserve the skillet).