Preheat oven to 425 degrees. Line a rimmed baking sheet with parchment paper.

Melt butter in a pan over medium-low heat. Add garlic and capers. Cook just until the garlic is fragrant, 30 seconds - 1 minute.

Place cod in the center of the prepared baking sheet. Place asparagus in bunches around the cod. Sprinkle with salt and pepper. Lay a lemon slice or two on top of each cod fillet and asparagus bunch.

Drizzle half of the caper butter over the top of the cod and asparagus. Bake in preheated oven for 15 minutes or until fish flakes easily and is cooked through.

Remove from oven and drizzle remaining butter over the fish and asparagus. Serve.