Preheat oven to 425F. Line a sheet pan with foil and grease.
Make a batter by whisking together flour, cornstarch, Rancher Rub, and milk. Mixture should be thick enough to stick to cauliflower florets.
Add cauliflower to the bowl with the batter and toss to coat all pieces.
Add panko bread crumbs to a second bowl. Remove cauliflower pieces from batter, shake off any excess, and the coat in panko. Place each breaded floret on the prepared baking sheet.
Spray the breaded cauliflower with oil. Bake for 20 minutes or until tender.
Drizzle cauliflower with Sweet & Sour Sauce and toss to coat. Return to oven for 5 more minutes.
Garnish with scallions and sesame seeds and serve with additional Sweet & Sour Sauce if desired.
