Sprinkle the pork chops all over with salt and the Cajun seasoning. Pour the flour into a shallow bowl. Dredge the chops in the flour, turning to coat, and tap off any excess. Reserve the remaining flour. Heat the olive oil in a large skillet over medium-high heat. Add the chops; cook until browned, 2 to 3 minutes per side. Transfer to a plate. Add the butter, onion, thyme and a pinch of salt to the skillet. Cook, stirring occasionally, until the onion is golden brown, 8 to 10 minutes. Add 2 tablespoons of the reserved flour to the skillet and cook, stirring, 1 minute. Add the chicken broth, bring to a boil and cook until reduced by one-third, about 2 minutes. Add the buttermilk and return the chops to the skillet. Bring the sauce to a simmer, then reduce the heat to medium low and cook until the sauce is thickened and the chops are just cooked through, 10 to 12 minutes. Serve with biscuits.