Preheat your oven to 425°F.
In a bowl, combine nonfat buttermilk, garlic powder, smoked paprika, salt, and pepper. Mix well.
Place the chicken breast in the marinade, ensuring it is well-coated. Cover and refrigerate for at least 30 minutes, or up to 2 hours for enhanced flavor.
Meanwhile, toss the green beans with olive oil, salt, and pepper, and spread them evenly on a baking sheet.
After marinating, remove the chicken from the buttermilk, allowing excess to drip off, then coat it with whole wheat breadcrumbs evenly on all sides.
Place the breaded chicken on a separate baking tray lined with parchment paper.
Bake both the chicken and green beans in the preheated oven. Roast the green beans for about 15-20 minutes, stirring halfway, until they are tender and slightly caramelized.
Bake the chicken for about 20-25 minutes, or until the internal temperature reaches 165°F and the coating is crisp.
Once done, plate the chicken alongside the roasted green beans and serve immediately.