Use paper towels to pat the halibut fillets completely dry -- this will ensure even browning. Season the fish on both sides with garlic powder, paprika, sea salt, and black pepper.

Heat the olive oil in a large skillet over medium-high heat for 2 minutes.

Add the fish fillets in a single layer (you can do it in batches if all the fish won't fit). Sear, without moving, for 3-4 minutes, until the edges of the fish are opaque. Flip and cook for 2-4 minutes, until cooked through.

Remove the fish from the pan and cover with foil to keep warm.

Reduce heat to medium-low. Add the butter to the same pan. Wait for it to melt, then heat for 2-3 minutes, stirring occasionally, until the butter is browned and smells nutty.

Squeeze all the juice from both halves of the lemon into the pan. Bring to a simmer, then reduce heat and cook for 3-4 minutes, stirring often, until the volume is reduced by half. The lemon butter sauce will still be thin, which is normal.

Drizzle a little lemon butter sauce over each serving plate. Place the pan seared halibut fillets over the sauce, then drizzle more sauce on top.