Place muffin pieces, cut sides up, in a 9×13 baking dish. Set aside.
Combine eggs, half-and-half, milk, brown sugar, orange zest, cinnamon, vanilla extract and salt in a blender.
Blend until thoroughly combined. Pour mixture over muffins in baking dish.
Lightly press down on muffins with a spoon to help saturate with liquid. Let soak, refrigerated, at least 1 hour.
Melt 1 tablespoon butter in a 12-inch oven-safe skillet (such as stainless steel or a well-seasoned cast iron pan).
Saute apple chunks for 2 minutes, stirring occasionally.
Add brown sugar and salt, and cook for 1 minute.
Transfer soaked muffin pieces to the pan with the apple mixture, arranging them in a spiral pattern with the flat cut edges down and the curved edges out. The pattern will resemble flower petals.
Pour the remaining custard over the muffin pieces.
When ready to finish the French toast, preheat oven to 425°F. Bake for 25 minutes, brushing with 2 tablespoons melted butter during last 5 minutes of baking.
Let stand about 10 minutes before serving. Lightly dust with powdered sugar, if desired.
Serve with warm maple syrup.