Heat the olive oil in a large skillet over medium-high heat until shimmering.
Season the scallops with salt and black pepper on both sides.
Carefully place the scallops in the skillet, making sure not to overcrowd the pan. Sear for about 2-3 minutes without moving them, until a golden crust forms.
Flip the scallops and add the butter to the pan. Cook for an additional 2-3 minutes until they are opaque and cooked through. Remove the scallops from the skillet and set aside.
In the same skillet, add the minced garlic and red pepper flakes (if using). Sauté for about 30 seconds until fragrant.
Pour in the lemon juice and stir to combine, scraping up any browned bits from the bottom of the pan. Let it simmer for 1-2 minutes.
Stir in the lemon zest and return the scallops to the skillet, coating them in the sauce.
Serve immediately, garnished with fresh parsley.