Remove fish from fridge 10 minutes before cooking. Pat completely dry on both sides.
Mix salt, pepper, garlic powder, smoked paprika, and onion powder. Season both sides of each fillet evenly.
Dust each fillet lightly with flour on both sides. Shake off excess.
Heat neutral oil and 1 tablespoon butter in a large skillet over medium-high. When butter foam subsides, add fillets presentation side down.
Cook 3–4 minutes without moving until deep golden underneath and releasing naturally from the pan.
Flip gently using a fish spatula. Cook 2–3 minutes until opaque all the way through and flaking easily.
Transfer to a warm plate. Do not clean the pan.
Reduce heat to medium. Add 4 tablespoons butter. When foaming, add garlic. Cook 1 minute until fragrant and barely golden.
Add broth. Scrape up all browned bits. Reduce 1 minute.
Add lemon juice, lemon zest, capers if using, and thyme. Stir and simmer 1 minute until slightly reduced and glossy.
Return fish to pan presentation side up. Spoon sauce repeatedly over each fillet for 30 seconds.
Serve immediately with fresh parsley, lemon wedges, and flaky sea salt.