Preheat oven to 425°F. Line a large baking sheet with parchment paper (or set a wire rack on top of the pan).
Pat cauliflower florets very dry with paper towels.
In a shallow bowl, combine panko, parmesan, garlic powder, paprika, onion powder, salt, and pepper.
In a second bowl, whisk flour and milk until smooth.
Dip each floret in the batter, let excess drip off, then roll in the panko mixture, pressing lightly to adhere.
Arrange florets in a single layer on the baking sheet. Lightly spray tops with cooking spray (or drizzle with olive oil).
Bake 18 minutes. Flip florets, then bake 8 to 10 minutes more until golden and crisp. Broil 1 to 2 minutes at the end if you want extra color.
Serve immediately with parsley, lemon wedges, and your favorite dip.