Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Peel and cube the sweet potato into 1/2-inch pieces, chop the broccoli into bite-sized florets, and slice the red bell pepper into strips.
Place the vegetables on the prepared baking sheet, drizzle with half of the olive oil, and sprinkle with a pinch of the sea salt and black pepper.
Toss the vegetables to coat evenly and roast in the oven for 20 to 25 minutes until the sweet potatoes are tender and the broccoli edges are slightly charred.
While the vegetables roast, season both sides of the chicken breast with the garlic powder, dried oregano, and the remaining sea salt and black pepper.
Heat the remaining olive oil in a heavy-bottomed skillet or cast-iron pan over medium-high heat.
Place the chicken in the hot skillet and sear for 6 to 7 minutes per side, or until the internal temperature reaches 165°F and the exterior is golden brown.
Remove the chicken from the pan and let it rest for 5 minutes to lock in the juices before slicing it against the grain.
Plate the sliced chicken alongside the roasted vegetable medley and finish with a bright squeeze of fresh lemon juice over everything.