Thinly slice the red bell pepper and dice the yellow onion.

Thinly slice the pepperoncini peppers into rings, or measure out the sliced pepperoncini.

Finely grate the Parmesan cheese or measure out store-bought grated cheese.

Cut the chicken breasts across the grain into 1/2-inch-thick slices and place in a large bowl. Season with 3/4 teaspoon kosher salt and black pepper, and toss to coat.

Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Add half of the chicken and cook until browned and cooked through, about 6 minutes. Transfer to a plate and repeat with remaining chicken.

Add the remaining 1 tablespoon olive oil to the skillet. Add the bell pepper, onion, remaining 1/2 teaspoon kosher salt, and Italian seasoning. Cook until beginning to brown, about 2 minutes.

Add the chicken broth and scrape up the browned bits from the bottom of the pan. Cook until the broth is reduced by half, about 2 minutes.

Add the Parmesan and heavy cream. Bring to a simmer and cook until slightly thickened and the peppers are tender, about 3 minutes.

Return the chicken and any accumulated juices to the pan. Add the pepperoncini and toss to coat in the sauce. Serve with additional Parmesan cheese if desired.