Preheat your oven to 400°F and line a baking sheet with parchment paper.
Peel and cube the sweet potato into half-inch pieces, then roast on the prepared sheet for 20 minutes until tender.
Season the chicken breast with half of the sea salt, black pepper, and the dried oregano.
Grill the chicken over medium-high heat for 6 minutes per side or until the internal temperature reaches 165°F, then slice into strips.
Slice the halloumi into thick slabs and sear in a dry non-stick pan for 1-2 minutes per side until a golden crust forms.
In a small jar, whisk together the olive oil, lemon juice, Dijon mustard, and remaining salt and pepper to create the dressing.
Place the arugula in a large bowl and top with the roasted sweet potatoes, grilled chicken, and warm halloumi.
Drizzle the zesty dressing over the salad and toss gently before serving.