Preheat oven to 350 degrees F. Combine flour, onion salt, onion powder, paprika, and cayenne pepper in a shallow baking dish. Season with salt and black pepper and stir to combine.

Heat olive oil in a large oven-proof skillet over medium-high heat. Pat the chicken dry and place in the flour-spice mixture, turning to coast lightly on both sides. Shake off excess.

Add coated chicken to the hot olive oil and sear until brown, 1 to 2 minutes per side. Remove to a plate.

Add chopped peppers and onions to the oil remaining in the skillet and reduce heat to medium. Season with salt and black pepper. Cook, stirring occasionally, until vegetables are limp, 5 to 7 minutes. 

Pour the remaining flour mixture from the baking dish into the skillet and stir to combine. Stir in the warmed chicken stock and increase heat to medium high. Bring to a boil. Reduce heat until the mixture simmers. Add the chicken and stir to combine with vegetables. Top each chicken breast with a slice of cheese, then transfer the skillet to the oven and cook about 30 minutes or until the temperature reads 165 degrees F when measured with an instant-read thermometer. Add additional warmed chicken stock or broth if desired to create more liquid for serving with a side dish. 

Taste, add salt and black pepper as needed. Serve over rice, orzo, or favorite pasta.