Mix together the dry rub ingredients. Pat the pork dry on both sides and heavily season both sides of the meat.
Mix together the maple syrup, balsamic and fresh thyme in a bowl. Set aside.
Turn oven on broil.
Heat a cast iron skillet over medium to high heat. When warm, add 2 Tbsp extra virgin olive oil. When it is shimmering, add the pork and cook for 3 minutes per side. Use 4 minutes if the pork is extra thick. When done, remove and set aside.
Add another 2 Tbsp of extra virgin olive oil to the pan and when shimmering add the onions. Cook stirring consistently for 4 minutes.
Add 1 cup of chicken broth and deglaze the pan, scraping all the black bits. Because it is a cast iron pan, bits and sauce might look more black than brown right now. Simmer until about 2/3 of the chicken broth has evaporated off (about 2-3 minutes).
Add the pork chop and plums back to the pan. Then pour the sauce over the pork chops and plums. Add the rosemary and make sure it is submerged in the sauce. Simmer for 5 minutes.
Spoon the sauce over the pork chops and put the whole pan in the broiler for 5-7 minutes depending on pork chop thickness.
If the sauce has become overly thick, add 1/3 cup of water. Serve with additional fresh thyme, sea salt and fresh cracked pepper to taste.