Preheat the oven to 425°F and line a large rimmed baking sheet with parchment or foil. Arrange a wire rack on the pan if you have one; it helps air circulate under the chicken for better browning.
In a large bowl combine the garlic powder, onion powder, smoked paprika, chili powder, kosher salt, black pepper and cayenne (if using). Toss the sweet potatoes, cauliflower and red onion with about 2 teaspoons of the oil and two-thirds of the spice mix until evenly coated.
Spread the seasoned vegetables in an even layer on one side of the prepared sheet pan. Roast 25 minutes, stirring or flipping the vegetables once halfway through so edges caramelize evenly.
While the vegetables roast, pat the chicken cubes dry. Toss the chicken in the remaining olive oil and the leftover spice mixture in the same bowl, then let rest 8–10 minutes to absorb flavors (this quick rest acts like a short marinade).
When the vegetables have about 5 minutes left of their roast time, remove the pan and push the veggies to one side. Scatter the seasoned chicken pieces in a single layer on the empty side of the sheet. Return the pan to the oven and roast another 12–15 minutes, turning the chicken once, until the pieces register 165°F and both chicken and veggies have golden-brown edges.
Mix the hot honey with the lemon zest. Drizzle or brush this mixture evenly over the chicken and vegetables. Sprinkle crumbled feta across the pan and add sliced jalapeño if using.
Set the oven to broil on high and broil the sheet pan 1–2 minutes—just long enough for the honey to bubble slightly and the feta to warm. Watch carefully to avoid burning.
Remove from oven, scatter the chopped parsley (or cilantro) over the top and let everything rest 3 minutes before serving so juices settle. Serve warm with extra hot honey on the side.