1. Heat olive oil in a large skillet over medium-high heat.

2. Season the chicken with salt and pepper, then coat it in flour.

3. Place the chicken in the skillet and cook until browned on both sides, about 5 minutes per side.

4. Remove the chicken from the skillet and set aside.

5. Add the diced onion to the same skillet and cook until softened, about 5 minutes.

6. Add the diced tomatoes to the skillet and cook until they begin to break down, about 10 minutes.

7. Return the chicken to the skillet and stir to combine with the tomato mixture.

8. Reduce heat to low and simmer for an additional 10-15 minutes or until the chicken is cooked through.

9. Serve hot.