Season pork chops with salt, thyme, garlic powder, and pepper on both sides.
In a 12 inch cast iron pan over medium heat, add olive oil. When hot, add pork chops and sear on both sides, about 1-2 minutes per side. Remove pork chops from pan and set aside.
Reduce heat to medium-low. Add onions to pan and cook until softened and deep golden brown, about 15-20 minutes. (If onions begin to dry out, add a splash of water to the pan to rehydrate. If onions look like they're going to burn, reduce heat further and add a splash of water.)
Add flour to onions and toss to coat. Cook for one minute, then add beef broth, stirring until incorporated, making a gravy.
Add pork chops back to pan and nestle into onions. Spoon onion gravy over pork chops. Top each pork chop with a slice of cheese, then transfer to oven. Bake for 14-15 minutes for 1.5" pork chops, or until center reaches 145 degrees Fahrenheit. Serve over mashed potatoes or with a side salad.
The thickness of your pork chops will alter the time needed in the oven.
For thin pork chops (½ inch or less): Oven finishing is not required. Cook for another 2-3 minutes on the stove top, allowing cheese to melt and pork chops to finish cooking through.
I highly recommend using a meat thermometer to check the temperature of your pork chops as they cook. This guarantees a perfectly cooked meat - every time.