Heat a large oven-safe pan or cast iron skillet over medium-high heat. Once hot, heat the oil in the pan.
Place the chicken breasts on the pan and sear each side for 2 minutes, until they're golden brown. Once you place them on the pan, don't move them. Transfer them out of the pan onto a plate, and turn off the heat.
Pour 1 cup of marinara sauce on the bottom of the pan. Using a spoon, spread it to make a base. Place the chicken breasts into the sauce.
Bake the chicken:
Bake the chicken breasts in the preheated oven for 25 minutes.
Load up the toppings:
Remove the skillet from the oven. Pour the reaming sauce over the top of the chicken. Sprinkle the cheese and then add the toppings like pepperoni and black olives. Swap your favorites here!
Place the skillet back in the oven for another 8 to 10 minutes, until the cheese has melted and the top is a nice golden color.
Serve!
Remove the skillet from the oven and serve the chicken breasts with the cheesy toppings and marinara sauce. Enjoy this dish with a side salad, pasta, or breadsticks!